Androgen secretion

Excess androgen secretion is responsible for 80% of women presenting with hirsutism. 

Cerebellar haemangioblastoma Massive uterine fibroids Androgen-secreting tumours Phaechromocytoma Autonomous red cell proliferation Primary proliferative polycythaemia... 

Extreme clinical examples of androgen excess include central precocious puberty, the adrenogenital syndromes, and androgen-secreting adrenal, ovarian, or testicular tumors. Less severe problems include idiopathic hirsutism, premenstrual syndrome, and severe cystic acne. 

Androgens are substances which cause development of secondary sex characters in males. The most important androgen secreted by testes is testosterone. Testosterone is synthesized from the cholesterol in testes mainly, under the influence of LH from pituitary. In peripheral tissues testosterone is partly converted into more active dihydrotestosterone. 

It is a natural androgen secreted by testis. The secretion is regulated by LH hormone secreted by pituitary gland. 

In humans, the most important androgen secreted by the testis is testosterone. The pathways of synthesis of testosterone in the testes are similar to those previously described for the adrenal and ovary (Figures 39-1 and 40-2). 

Control of androgen secretion and activity and some sites of action of antiandrogens (1), competitive inhibition of GnRH receptors (2), stimulation (+, pulsatile administration) or inhibition via desensitization of GnRH receptors (-, continuous administration) (3), decreased synthesis of testosterone in the testis (4), decreased synthesis of dihydrotestosterone by inhibition of 5a-reductase (5), competition for binding to cytosol androgen receptors. 

There is a risk of myocardial hypertrophy in children on prolonged treatment with ACTH (2), an effect that could reflect increased androgen secretion and thus be more likely to occur than with glucocorticoids. 

Androgen secretion due to corticotropin can cause virilization in women (24). 

Control of androgen secretion and activity and some sites of action of antiandrogens. (1),... 

Androgenic effects Androgenic steroids are used in males with inadequate androgen secretion. [Note Hypogonadism can be due to Leydig cell dysfunction or, secondarily, to failure of the hypothalamic-pituitary unit. In each instance, androgen is indicated.]... 

After hypophysectomy there is a rapid loss of LH receptors and androgen secretion by the testis. Treatment with LH alone will restore Leydig cell steroidogenesis but also causes even further decreases in testicular LH receptors. Continued treatment with LH alone leads to Leydig cell hyperplasia and an increase in LH receptors. However, even with marked Leydig cell hyperplasia in response to sustained elevations of endogenous LH, as in the tfm rat (see Ref. 6 for other references), the LH receptor content of the testis remains subnormal. 

In adrenogenital syndrome and adrenal virilism, an attempt may be made to suppress excess adrenal androgen secretion by inhibiting pituitary corticotropin production by means of prednisolone or dexamethasone. Suppression of androgen production is effective if there is adrenal hyperplasia, but not if an adrenal tumour is present. Hairiness, which women especially dislike in themselves, is often unaffected even though good suppression is achieved, and menstruation recommences. 

Testosterone is the natural androgen secreted by the interstitial cells of the testis it is necessary for normal spermatogenesis, for the development of the male secondary sex characteristics, and for the growth, at puberty, of the sexual apparatus. It is converted by hydroxylation to the active dihy drotestosterone. 

Spironolactone (p. 534) also has antiandrogen activity and may help hirsutism in women. Androgen secretion may be diminished by continued use of a gonadorelin (LH-RH) analogue (see p. 714). 

Age and familial factors in both men and women influence both plasma adrenal androgens (DHEA and DHEA-S). Adrenal androgen secretion starts to rise about the age of 9, peaks at about age 25, and declines after age 30. In the seventh decade of fife, the adrenal androgen concentrations fall to prepubertal concentrations. Thus in the elderly, the circadian variation in plasma DHEA is relatively blunted and dissociated from the circadian variation in cortisol. The adrenal contribution of serum androstenedione declines with age. DHEA and DHEA-S responses to stimulation with exogenous ACTH are... 

Mineralocorticoid and adrenal androgen secretion is also circadian and episodic in nature, but the dynamic swings in concentrations are not as pronounced as with cortisol. It is usually recommended, however, that blood samples for adrenal steroids be collected in the 0700 to 1000 hour tune frame for consistency in result interpretation. 

The responses of adrenal androgen secretion to ACTH stimulation are variable. Plasma DHEA and androstenedione increase threefold to fourfold after 90 minutes of stimulation with ACTH (i0 lg/m ). DHEA-S, on the other hand, increases 30% to 50% with ACTH administration. ACTH stimulation studies are not considered useful in evaluating hypoandrogenic disorders. 

Meilde AW, Daynes RA, Araneo BA. Adrenal androgen secretion and biologic effects. Endocrinol Metab Clin North Am 1991 20 381-400. 

Odell W, Parker J. Control of adrenal androgen secretion. In Genazzani AR. Adrenal androgens. New York Raven Press, 1980 27-42,... 

Parker LN. Control of adrenal androgen secretions. Endocrmol Metab Chn 1991 20 401-22. 

Androgens are a group of Cit, steroids (Figure 53-2) that cause masculinization of the genital tract and the development and maintenance of male secondary sex characteris-tics. They also contribute to muscle bulk, bone mass, libido, and sexual performance in men. Testosterone is the main androgen secreted by the Leydig cells of the testes, and its production increases during puberty. Women produce about 5% to 10% as much testosterone as do men. 

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