Endocrine, Glands

ENDOCRINE, GLANDS. - In contrast to the glands of external secretion, which elaborate ferments with biochemical activity (secreta) or eliminate materials that are unusable or harmful to the organism (secreta), there exist glands of internal secretion (e. g.) which pour their elaborated products directly into the circulatory stream by means of the blood or lymphatic vessels that pass through them; these products take the name of "hormones" (ὄρμᾶς = I excite) because of their stimulating action on the most disparate organs and on the autonomic apparatus of vegetative life.

Through the work of these regulators of the vital processes, whose action stands alongside that of the enzymes (v.), the vitamins (v.), and certain metals and metalloids present in the organism, capable, even in minimal quantities, of significant biological actions (oligodynamic activity), there becomes possible that admirable and perfect unity of action which, even amid the myriad of cellular elements and the great number of organs and functions, appears in the human organism in functional equilibrium. Such unity rests on the one hand on the coordinating function of the nervous system, particularly of vegetative life, and on the other on the humoral equilibrium of the fluids circulating in the body (blood, lymph, cerebrospinal fluid and that of the cerebral ventricles), of whose exceedingly delicate physical, chemical and biological composition the aforesaid elements are factors.

In this scheme of actions the glands of internal secretion should be conceived, more than as organs of labor, as exceedingly delicate apparatuses of regulation and coordination of the vital functions. Their work manifests itself: through a morphoregulatory activity, if it stimulates, inhibits, orients and coordinates the building of the bodily mass or the morphological differentiation of the individual organism, orienting it toward this or that constitutional type (v. CONSTITUTION); or a chemioregulatory activity, activating or moderating the complex chemistry that underlies the vital phenomena; or a neuro-psychoregulatory activity on the great neuro-vegetative complexes (sympathetic-parasympathetic) or, indeed, on the nervous functions that underlie the highest processes of psychic life and on the equilibrium of the cortical and subcortical nervous centers of intelligence and emotionality.

At present the endocrine apparatus and the various glands that constitute it are not yet known in their entirety; of some we seem to know a great deal, others barely appear on the horizon of knowledge. Among the best known are cited: the hypophysis, the thyroid, the parathyroids, the adrenal glands, the endocrine portion of the pancreas (the site of Langerhans), that of the sexual glands (testicle, ovary); the thymus and the epiphysis, certainly endocrine organs, are perfectly known. To these producers of hormones many others will undoubtedly have to be added later; already some authors count among them certain particular functional aspects of the liver (the antianemic hormone of the liver, or Asher's hepatic hormone), of the spleen, of the tonsils, of the intestinal mucosa, of the kidney, etc.

A complete study of the e. g. and of their hormones would go beyond the established plan; a brief functional profile of the most important will therefore suffice, above all to bring into view the interferences that each of them can have with regard to the higher psychism (emotional, intellectual).

I. THE HYPOPHYSIS OR PITUITARY GLAND

It is the size of a pea or a small bean, weighing barely about half a gram, placed (in a socket [sella turcica] hollowed out at the expense of the underlying ethmoid bone) at the base of the encephalon, with which it establishes particular relations through a stalk (infundibulum) that joins it to the diencephalic zone of the brain, the seat of the higher nerve centers of vegetative life and indirectly connected with the centers of emotional life. Being in such close relations with the nerve centers and the possibility of having almost all the other glands of internal secretion under its control, by means of its hormonal complex, places the hypophysis on a particular plane of functional privilege that has earned it the names of "endocrine brain" or "glandular orchestra leader." It is composed of three portions: an anterior one that is clearly glandular, a posterior one of nervous nature, related in development to the brain and in synergy of action with the diencephalic apparatus, and an intermediate one of ependymal nature, poorly developed in man. The anterior lobe (prehypophysis), rich in so many hormones that the functions of the organism escaping its action may be said to be few, elaborates: a growth hormone, which stimulates the development of body mass particularly in the sense of height, whence, if in excess during the age of growth, gigantism, and acromegaly once development is complete; hormones stimulating the thyroid and the cortex of the adrenals; regulators of the endocrine function of the pancreas; stimulants of the liver to release its reserve of hepatic glycogen (diabetogenic hormone); of the mammary glands to secrete milk during the puerperium (prolactin); the gonadotropic hormones (gonadin A and B) which promote or inhibit the specific activity of the germinative tissues and of the endocrine tissues of the sexual glands.

The posterior portion of the hypophysis gives rise to a hormone that restrains urinary secretion (the deficiency of which produces "diabetes insipidus," polyuria without glucose); a hormone (vasopressin) capable of raising arterial pressure in relation to the contraction of the small capillary arteries; oxytocin which, having reached a particular concentration in the blood toward the end of pregnancy, provokes the expulsive contractions of the uterus. The intermediate lobe, of lesser importance in man, produces intermedin, which, particularly in certain animals, acts by modifying the size of the pigment cells of the skin, so as to produce on the skin patches of varying size, configuration and color (the "nuptial livery" of the male bitterling during the mating period); even in the human species it seems that this hormone has a relation to the generative function, producing the increased pigmentation characteristic of particular zones of the skin in the state of pregnancy. This suffices to make us realize how much the hypophysis weighs in the economy of the entire organism and how necessary a perfect quantity and mixture of its manifold hormones is, so that the organism, in a just equilibrium of development, may avoid the two opposite anomalies of gigantism and dwarfism; so that equilibrium may be preserved in the complex interplay of the germinative and endocrine activity of the sexual glands, in pregnancy, in childbirth, in lactation; so that adipose tissue may be deposited in normal quantity or with the proper topographical characteristic; for the normal turnover of water in the organism, a condition of a regular intake and output of saline substances, particularly sodium chloride; for the metabolism of sugars; for the equilibrium of waking and sleep, which may prevent the most stubborn insomnia or the state of lethargic hypersomnia; for an optimum of arterial pressure, etc.

But no less is the importance of the hypophyseal hormones as regards the neuropsychic and intellectual manifestations of the individual. The equilibrium of affective life, a normal development of the intelligence, and above all its particular characteristics, are bound to the functioning of the hypophysis; the neuropsychic temperament, the disposition variable according to the "individual type," receive their imprint from a functional excess or deficiency of the hypophysis. All this must be kept in mind in education and in formulating a moral judgment of the individual.

II. THE THYROID

It is situated in front of and to the sides of the larynx and the first rings of the trachea, and ranks immediately after the pituitary in importance; first among all the others, it has earned the name "queen of the endocrine glands." The functions of its hormone are numerous, with points of action on both vegetative and relational life. Through its morphoregulatory activity, the thyroid hormone influences the development of many tissues: connective, cutaneous and its appendages (hair and nails), skeletal, blood elements, nervous system, other glands. Among other things, the regulation of biochemical activities — the substrate of the phenomena of vegetative and relational life — is assigned to the thyroid; it directly stimulates oxidative processes and indirectly, through the sympathetic system, the traffic of material and energy exchanges that take place between the organism and the environment surrounding it (metabolism), particularly with regard to fats, nitrogenous substances, water, salts, carbohydrates (glycogen), just as it influences the production and regulation of body heat. Of very particular importance is the stimulating action which, likewise through the sympathetic system, is exerted on the nervous activities of the organism, both neurovegetative and those of relational life, whence the special importance of the thyroid for the development and the characteristics of the individual's psychic functions (hyperemotionality, readiness and rapidity of action and ideation).

The thyroid maintains relations of collaboration (synergy) with the germinal portion of the genital glands, the medulla of the adrenals, the anterior pituitary; of opposition (antagonism) with the thymus, the pancreatic islets, the parathyroid, the adrenal cortex, the posterior pituitary. The already mentioned bioregulatory elements (vitamins, oligodynamic minerals) establish links with it: vitamins A and B hinder its function; in the blood, the increased content of iodine, with which the principal hormone of the thyroid (tyrosine) is very rich (95.5%), intensely stimulates its action; violent emotional states, capable even of doubling the iodine content of the blood, promote the action of the gland, producing in the individual an accentuation of the catabolic phase of metabolism, thinness and nervousness; a particular excitatory action is exerted by nicotine (the thinness and nervousness of smokers).

A hyperfunction of the thyroid, which exceeds the limits of a normal individual variability, gives rise to the picture of "Flajani-Basedow disease" or "exophthalmic goiter," more frequent in the female sex (6:1) and in youth (20-40 years). In this disease, a hyperfunctioning enlargement of the thyroid is accompanied by an exaggerated increase in the pulse rate, up to over 100 (tachycardia), the bulging of the eyeballs, excessively protruding between the widened palpebral fissure (exophthalmos), an exaggeration of the internal oxidation processes with a greater consumption of oxygen, the prevalence of the catabolic phase of metabolism, at times accentuated to extreme emaciation. Some other ocular symptoms, tremor of the outstretched hands, excessive sweating, alterations of the skin and of the cutaneous appendages, disturbances of intestinal function (diarrhea, etc.) complete the picture of pathological hyperfunction of the thyroid. A diminution of thyroid activity, which falls below normal individual variability, gives rise, conversely, to the picture of so-called myxedema, a particular form of elastic swelling of the skin, combined with a slowing and a more or less serious decline of all the functions of vegetative and relational life, with deficiencies of bodily development, so that, if the defect has existed since birth, the individual remains a dwarf. The nervous system and the psychic activity of the subject suffer in a particular way, in whom there appear torpidity of action, mental apathy, up to the most absolute lack of intelligence (cretinism). Often the picture is completed by an engorgement of the thyroid in its supporting connective part which, with its exaggerated development, suffocates the secreting portion of the gland; hence the characteristic protrusion at the front of the neck, that is, the goiter. This, combined with hypofunction of the thyroid and a more or less serious degree of cretinism, constitutes a disease and an endemic character in certain mountainous regions of Switzerland, the Pyrenees, Germany, Savoy and in Italy in Piedmont (Val d'Aosta), in Lombardy (Valtellina), in certain zones of Liguria, Sicily and Sardinia. The cause of endemic goiter is still debated; according to some authors, the phenomenon would be due to the presence of particular goitrogenic substances, in a colloidal state, contained in the waters drunk locally (gypsum, fluorine); N. Pende speaks of "endemic disease of the mountains" and admits multiple causes (scarcity of iodine, of solar radiation, of certain foods, of hygiene, consanguinity in marriages, etc.). Because of the aforementioned relations existing between the thyroid and the sexual glands, in thyroid hyperfunctions there is a failed or delayed pubertal development with a more or less marked deficiency of the primary and secondary sexual characteristics. In hyperthyroidism, on the contrary, precocious sexual transformation. The functional equilibrium of the thyroid or its shift toward excess or defect, within the limits of a normal individual variability, impresses particular constitutional characteristics on the organism, deflecting it toward the longilineal (v.) or brevilineal (v.) type, just as it orients it differently with regard to temperament and character.

III. THE PARATHYROIDS

They are located posteriorly, close against the thyroid, normally four in number, about the size of a grain of rice, and, despite their smallness, they weigh so heavily in the endocrine balance of the individual that their removal leads to the gravest consequences. Their function has been sufficiently clarified that its very great importance appears as regulators of the mineral metabolism of calcium and phosphorus, elements fundamental for the mechanical equilibrium of bone tissue and the biochemical equilibrium of the nervous system. Bones owe their rigidity, capable of giving the organism the necessary firmness and resistance in its form, to calcium carbonate (10%) and tricalcium phosphate (90%). The nervous system undergoes variations in its excitability, in relation to the variation of the molecular equilibrium of the mineral salts dissolved in the blood plasma: calcium, in union with magnesium, exerts a sedative action on neuromuscular and psychic excitability, while sodium and potassium, on the contrary, increase its irritability. All of life thus comes to gravitate between these two "chemical poles" (Rondoni): on one side athenicity, that is, diminished neuromuscular excitability, due to the prevalence in the osmotic equilibrium of the circulating fluids of the calcium-magnesium pair; on the other, the prevalence of sthenicity, an increase of neuromuscular excitability, due to the prevalence of the sodium-potassium pair. In all this, the delicate regulation of the exchanges and of the equilibrium of calcium marks the wonderful importance of the parathyroids in the economy of the organism.

In parathyroid deficiency, owing to the diminished quantity of calcium circulating in the blood (hypocalcemia) compensated by an increase of phosphorus (hyperphosphoremia), the bones do not acquire and lose calcium while neuromuscular irritability increases, up to the forms of spastic and convulsive contraction of tetany, eclampsia, and spasmophilia. Signs revealing a deficient function of the parathyroids may be: fragile and grooved nails, defects of the enamel of the incisor teeth, the so-called bags under the eyes, the tendency to grimaces, to facial "tics," the rolling of the eyes, certain forms of migraine, asthma, neuralgia, the tendency to swelling. Particular morbid forms are produced by a state of hyperfunction of the parathyroids (osteitis fibrosa or Recklinghausen's disease).

The parathyroid hormone is linked by relations of collaboration with vitamin D₃ (the calcium-phosphorus-fixing vitamin) and with other hormones, such as those of the thyroid and of the thymus.

IV. THE ADRENAL GLANDS

There are two of them, situated like a cap, one on each side on the upper pole of the kidneys, the size of a few centimeters (maximum: cm. 6 x 3 x 1); for their specific activity they have earned the name of "glands of energy." Each adrenal gland does not constitute a single organ, but unites in itself a cortical portion (cortex) and a medullary portion (medulla), each elaborating different hormones.

The cortex, once held to be anatomically and functionally unitary, has been revealed by modern studies to be made up of three different zones: the "glomerular" zone, whose hormones (the most important: deoxycorticosterone, the only one currently obtained by synthesis) regulate the hydroxylin metabolism, causing the retention of sodium (sodium chloride and table salt) and of water in the tissues and the elimination of potassium with the urine; moreover they increase arterial pressure. The "fascicular" zone produces another group of hormones, among which is remembered corticosterone, which regulates the metabolism of sugars and their formation at the expense of proteins, manifesting, if in excess, a diabetogenic action with an increase of blood sugar and its elimination with the urine. The "reticular" zone likewise elaborates a certain number, still not well defined, of substances, e.g., androsterone with an action equal to that of the sex hormones, in a predominantly male quantity, far less female; their effects appear in cases of hyperfunction of the adrenal cortex. The first two groups of adrenocortical hormones are truly indispensable for life: their complete deficiency produces "Addison's disease" or "bronze disease" which, within a few years, leads the individual to cachexia and death. It is very rare in childhood; in a high percentage of cases it is due to tuberculosis of the adrenals; clinically it manifests itself as a progressive intense loss of weight, neuromuscular weakness, lowering of arterial pressure, decrease of sodium chloride and of sugar in the blood, inconstant disturbances of the sexual sphere (impotence, amenorrhea), diminished resistance of the organism to harmful toxic and infective causes, a particular brown coloration of the skin and of the mucous membranes (whence the name), loss of hair particularly in the axillary and pubic regions. Hypercorticalism, which from total cases (Cushing's disease) to cases of partial hyperfunction presents the greatest symptomatic variety of intensity and combinations, is based on the already described characteristic activities of the glomerular, fascicular and reticular zones. In it the symptom "hypertrichosis" (exaggerated development of hair) always appears characteristic, not only on the trunk and on the limbs, but also, in women, on the face. In relation to the hyperfunction of the reticular zone and to the exaggerated quantity of incest with sexual activity (particularly of the androgenic and masculinizing fraction, more difficultly of the feminizing or estrogenic one), in partial hypercorticalisms one can see the various pictures of alterations of the individual's sexual habit, both with regard to primary and secondary characteristics, in the form of "adrenal virilism," of "adrenal feminilism," of "precocious puberty" combined with Addison's disease. In the first, if the hyperfunction of the reticular zone was established in an individual of the female sex, during fetal life, one sees a picture of "pseudohermaphroditism" whereby the individual (gynandroid) is at the same time a bearer of female sex glands (ovaries) and of external sexual organs of the opposite sex (v. HERMAPHRODITISM); if it was established before puberty, the picture of "heterosexual precocious puberty" or of "prepubertal virilism" appears; in already adult women it causes an addition of masculinizing notes to the previous female characteristics; in the male, androgenic hypercorticalism, which begins before puberty, manifests itself with a precocious appearance of it. In some cases, in the adult male, through a particular excess of estrogenic hormones, "adrenal feminilism" may occur with loss of the male characteristics and deviation toward the female type. On the other hand, cases are known in which an atrophy of the fascicular and glomerular zones, united with hyperfunction of the reticular zone, leads to the form of pseudohermaphroditism or of precocious puberty that unfolds in the picture of an Addison's disease.

If these are the nodal aspects of pathological hypo-and hypercorticalism, one may admit, in the physiological functional equilibrium of the adrenal cortex, a whole graduated series of ectypes staggered between the boundaries of fluctuating individual variability which, while giving us the explanation of many constitutional, functional and neuropsychic anomalies, show us the immense importance of these studies with regard to the educational and moral orientation of the individual, and the moral judgment of his actions.

The adrenal cortex has close relations of synergy with vitamin C, A, B₆; its hormones with regard to the regulatory apparatus of vegetative life have a vagotonic function (v. NEUROVEGETATIVE, SYSTEM).

The medullary substance of the adrenals exerts its hormonal function in the production of adrenaline or suprarenin with a hypertensive action, which effectively stimulates the sympathetic portion of the autonomic apparatus of vegetative life; it is extremely active, capable of making its specific action felt on the sympathetic even while being in the blood at a dilution of one to a billion; on the frog's heart it is active even when diluted in the ratio of 1:1,000! It is used, in the form of an intracardiac injection, to stimulate the revival of the heart in cases of its sudden paralysis.

V. THE SEXUAL GLANDS

Alongside the germinal epithelia that produce the sexual elements (spermatozoa, ova), destined for the procreation of the new individual, these glands also possess a part with the value of endocrine organs.

The endocrine testicle is constituted by "interstitial cells" nestled among the tangle of the seminiferous tubules in which the sexual elements originate; they have an undoubted endocrine value, producing a hormone (interstitial hormone or testosterone) whose action manifests itself to the advantage of the procreative function and of the general organic equilibrium. In fact testosterone, passing into the circulation, promotes at the time of puberty (v.), which in man is reached between the ages of 15 and 18, the perfecting of the primary sexual characters, already present at birth, and the development of the secondary sexual characters proper to the respective sex; at the same time it feeds the "libido" and the "potentia coeundi". With regard to its general action, testosterone excites catabolic metabolism, particularly of fats, exerts a tonic and sthenic neuromuscular action (a restorative action in neurasthenia), a psychotonic and psychosthenic one, which promotes the qualities characteristic of the virile age, activity, boldness, liveliness, and acuteness of the psychic processes, hindering, according to N. Pende, solely along with other glands (anterior hypophysis, thyroid, thymus), the onset of physical and psychic aging (slackening of the great organic functions, arteriosclerosis, myocardial weakness, diminished resistance to fatigue and to physical and psychic traumas, psychic depression, discouragement, diminished combativeness).

A negative demonstration of the hormonal action of testosterone is given us by castration. In individuals thus mutilated (eunuchs), if the deprivation occurred before puberty, there follows an arrest of development of the primary sexual characters, failure of the secondary ones to appear, with evident and persistent notes of physical and psychic infantilism, often with excessive lengthening of the body (gigantism); moreover the masculine psychic characteristics are lacking; so are the "libido", the "potentia coeundi" and "generandi". In the adult, as a result of castration, the primary sexual characters tend to regress; for some time, at times even for a long time, the "libido" and the "potentia coeundi" may persist, sustained by a residue of hormonal charge of the testicles, by the cortico-adrenal hormones and by the neuro-psychic mechanism of the acquired habit; the secondary sexual characters are also damaged: the beard hairs become sparse and fall out completely, adiposity with a feminine topography develops (breasts, pubis, hips), the voice takes on a high, feminine timbre, the temperament tends to lose its virile characteristics, becoming soft and feminine, the intelligence does not suffer from it—indeed it may become more acute—often the individual slides into psychasthenia and melancholy. The efficacy of the surgical transplantation in man of the testicles of an anthropomorphic ape (the Woronoff operation [v.]) is based on the general action of testosterone.

The ovary likewise possesses, in the likeness of the testicle, well-determined and very important endocrine functions linked to the cells of the walls of the oophoric follicle

(Graafian follicle) and to the corpus luteum. The former, by virtue of their internal secretion (folliculin), promote the perfecting of the primary sexual characters already formed at the moment of birth; the appearance and development of the secondary sexual characters in the period of puberty, in woman between the ages of 13 and 15; they feed the "libido", albeit in that more moderate form usually observed in woman. The entry into action of folliculin at the beginning of puberty is marked by the appearance of the first menstruation, which is then repeated periodically at every maturation of an ovum (on average every 28 days in 70% of cases), for the entire duration of female sexual life, up to the time of the menopause (v. CLIMACTERIC, AGE) at about 45-56 years, and at times 55-60, the extreme limit of 65 being very doubtful.

The menopause marks the arrest of the folliculinic function of the ovary; once this has occurred, the characteristics of femininity gradually regress: the change of the external forms, the growth of hair on the face, the sharpening and lowering of the tone of the voice, the modifications of the temperament imprint on the woman increasing notes of masculinization, which tend progressively to shorten the distances that separated the two sexes.

Alongside the action of folliculin, that of the corpus luteum must be remembered, an endocrine formation that periodically comes back to life, at every rupture of a Graafian follicle, in the empty follicular cavity. The hormone secreted by it (progestin or progesterone or luteosterone), chemically akin to testosterone, is the guardian of pregnancy (v.), since, in the period of about 12-16 days that intervenes between the rupture of the follicle and the eventual approaching menstruation (should the ovum not have been fertilized), progestin promotes in the uterine mucosa modifications such as to render it a terrain suitable for the implantation and development of the egg; these favorable modifications are maintained by the corpus luteum for the first four months of pregnancy, if the ovum was fertilized; for the remainder of the gestation, the guardian activity of the corpus luteum is assumed by the endocrine function of the placenta. Until the fourth month, the action of the corpus luteum is flanked by that of "vitamin E" or "antisterility vitamin". It should be recalled that the endocrine activity of the follicle and of the corpus luteum is under the control and stimulation of the gonadotropic hormones A and B of the anterior hypophysis and of a sexual nerve center.

VI. THE PANCREAS

Located in the abdomen in the loop formed by the first portion of the intestine (duodenum), besides being a gland that secretes the digestive juices, through its "islets of Langerhans" it is an endocrine organ that manufactures insulin, the hormone that regulates the metabolism of carbohydrates (sugars, starches) in glycogenesis, that is, their transformation and storage in the form of "glycogen" in the liver cells and in the muscles, and in making the utilization by the cells of the portion of sugar dissolved in the blood more complete. The antagonist of insulin is the already mentioned adrenaline, the hormone of the medulla of the adrenals, which stimulates the mobilization and the destruction of hepatic glycogen (glycolytic function), thus leading to an increase in the percentage of glucose (in the normal individual about 1 per thousand) present in the circulating blood.

If one considers that carbohydrates are par excellence our dynamogenic foods, fuel that, through its oxidation within the tissues, particularly the muscular ones, is the source of the energies we expend, one can realize what the importance is of the endocrine balance insulin-adrenaline as regulator of the accumulation-utilization mechanism of carbohydrate substances. Vitamins B₁, B₂, C and zinc in oligodynamic function are in a relationship of collaboration with insulin.

VII. THE EPIPHYSIS OR PINEAL GLAND

It is about the size of a large pea, weighing barely a quarter of a gram, situated above the thalamus of the brain, between the corpus callosum and the cerebellum, symmetrically to the hypophysis situated below; it too enters into very particular relations with the third ventricle, the seat, as has already been said, of important nervous centers regulating vegetative life. Its hormone may still be considered unknown in its constitution, but not in its action, particularly ticularly important in the first period of the individual's life. The epiphysis acts on the sexual glands, with an action opposed to that of the hypophysis; in fact, while the latter, as is already known, through the gonadostimulins, promotes the activity of the gonads, the epiphysis, which deserves the name of "guardian of childhood," through an anti-gonadotropic hormone, prevents pubertal development and sexual differentiation; hence, from the tenth year of age, in relation to the preparing and subsequent unfolding of the individual's sexual development, the gland undergoes a natural process of atrophy and functional regression. Confirmation of this lies in the fact that the experimental extirpation of the epiphysis in animals, and its destruction before the tenth year of life in man, through the action of morbid lesions that affect it, particularly tumors, leads to exaggerated bodily development and precocious puberty (pineal macrogenitosomia, hypergenitalism) with gradual, increasing, full appearance of the primary and secondary sexual characteristics, and the appearance of menstruation in girls even in the very first years of life. It seems that epiphysis preparations prove useful in schizophrenia and are capable of making hair growth more active.

The epiphysis protects the existence of the thymus, which is condemned by it to gradual atrophy through the awakening of the activity of the sexual glands; it is in functional opposition to the anterior portion of the hypophysis, the sexual glands, the thyroid, and the adrenal cortex.

VIII. THE THYMUS

It too is a gland proper to youthful age, as is shown by the progressive decrease in its relative weight as one approaches puberty, the time at which it rapidly undergoes atrophy; it is situated in the anterior mediastinum, enclosed in the thorax between the sternum, the heart, and the two inner surfaces of the lungs; in common language it is called "animalia"; Gifeno considered it the seat of courage and of the emotions.

While the inner portion of the thymus is formed of lymphoid tissue, akin to the lymphatic glands, the medullary portion (Hassall's corpuscles) is the truly endocrine part, producing the thymic hormone, which, although not yet certainly isolated and identified from the chemical point of view, is known empirically in its actions: excitation of the anabolic phase of metabolism, chiefly with regard to glucose (cooperation with insulin), with an increase in body mass, particularly during the periods of "turgor" of endouterine and pre-puberal life (v. ETÀ DELLA VITA). In cooperation with vitamin D₃, the thymic hormone facilitates the uptake of calcium and phosphorus on the part of the skeleton; supporting and protecting the action of the epiphysis, it acts as a check on the puberal development of the gonads, and thus stands in functional opposition to the anterior portion of the hypophysis, the sexual glands, and the adrenal cortex. Exaggerated function of the thymus (Pende's constitutional hyperthymic syndrome) leads, in a large percentage of cases (45%), to cryptorchidism (v.); it causes excessive bodily development (macrosomia) and of fat, with puerile somatic, sexual and psychic characteristics; exaggeration of the infantile lymphatic state (adenoid vegetations, tonsillar and splenic hypertrophy, a tendency to exudative skin conditions, etc.). On the contrary, removal of the gland in young animals or its deficient development in the child produces arrest of bodily development, particularly in height, and defective calcification of the bones, which remain soft and pliable.

The thymic hormone, with regard to the neurovegetative system, has an excito-vagal action, in opposition to the sympathicotropic action of adrenaline; in hyperthyroidism (Flajani-Basedow disease) there is marked thymic hypertrophy and hyperfunction, in the attempt to counterbalance the hypersympathicotonic state and the accentuation of the catabolic basis of metabolism. These are the most important and best known g. e.; of others one can only glimpse the existence or surmise the function.

IX. CONCLUSION

Given what has been said, one must insist on the great importance of the function of the endocrine apparatus for all the phases of the organism's development, from the first moments of intrauterine life, in which it is affected by the action of the mother's hormones, and subsequently, through its own, along the ascending path of infancy, adolescence and youth, in the state of equilibrium of maturity, and in the regression of old age; this applies both to the lower manifestations of vegetative life and to the higher ones of the life of relations, up to those that accompany and are the instrument of the psychic functions of feeling, intelligence and will.

Because of the collaborative relationships that enzymes and elements derived from the vegetable environment (vitamins) and the mineral environment (metal ions, oligodynamic minerals) establish with hormones, the organism finds itself immersed in, sustained by, and to some extent determined by a complex atmosphere of physical and biological causes that interweave and subordinate to one another the life of the macrocosm and the microcosmic life of our organism. Although some of these causes, particularly the vitamins and the mineral ones (and here one must not forget even the meteorological ones), up to a certain point act in the same way upon that group of organisms living in a given environment, one sees how, in fact, each responds differently, so that from this arises that almost infinite variability of the various individual morphologico-functional types proper to living beings. This is due to the action and mutual equilibrium of the endocrine glands which, like a "constellation" (N. Pende), establish themselves in a determinate equilibrium for each organism; this is due to the hereditary ground upon which the whole complex of such causes acts, particularly upon the tissue that is at the apex of the organic hierarchy, that is, upon that of the encephalic nerve centers. "If the organic ground, if the various tissues, upon which the said neurochemical constellation regulating life must act, present hereditary and acquired structural alterations, then the hormonal actions, like the vitaminic ones, cannot have a normal response on the part of tissues already abnormally constituted. This is the fundamental principle to be kept in mind above all for the understanding of the relationships between neuropsychopathology and endocrinology or vitaminology, and for the applications of hormonal and vitaminic treatments to the diseases of development, of metabolism, of the nervous system, and of the psychic sphere" (N. Pende, La scienza moderna della persona umana, Milan 1947, p. 93).

Giuseppe de Nino