SEXUALITY AND AGING: ENDOCRINE AND REPRODUCTIVE TRACT CHANGES IN MALES
Changes in endocrine function and reproductive structures are more gradual, less pronounced, and seem to occur somewhat later for males than for females. Unlike females, males have no abrupt change of life.
Circulating androgens in males are relatively constant after puberty, showing only gradual declines until about age forty or forty-five. After the mid-forties, androgen levels are about 55 to 60% of what they were earlier. After age sixty-five, values are about 30% of those in the thirties. In advanced age, about seventy-five, androgens have dropped 85 to 90% compared with levels before thirty. Paschkis reported 8 to 20 mg/day total urinary 17-keto-steroids in sexually mature males; values of less than 5 mg/day were not uncommon among elderly men. The fact that aging affects testicular cells known to produce androgen and correlates in time with declining androgen levels is taken as evidence that declining androgen levels are primarily a result of testicular decline. Because androgen levels decrease in both males and females (Dorfman and Shipley), it suggests that the adrenals may also be involved (Gherondache).
Conclusions about pituitary activity in males parallel those for females. Although gonadotropin levels are not as high in aging men as in aging women, there is evidence of increased anterior pituitary activity. Paschkis reported 4 to 24 mouse weight units of urinary gonadotropins as typical of his sample of sexually mature males under fifty. In subjects in their sixties and seventies, amounts up to 96 m.w. units have been found.
It is debatable whether there are significant changes in estrogen levels in males. Pincus reported no change in total estrogen levels, although specific estrogen groups showed some decline. Gherondache has reported that total estrogen output in aging men is reduced by about 30$ and progesterone output declines about 60%.
Compared with young men, testicles of males fifty-five and older seem smaller and less firm (Rubin). Although there is little change in testicular weight with age, there are marked changes in testicular tissue. The number of Leydig cells decreases progressively with age and changes as early as twenty-five or thirty years have been observed in some men (Tillinger). The reduced number of secretory cells follows rather closely the lowered levels of androgen, suggesting a functional relationship. The lipid content of Leydig cells decreases after the fourth decade (Lynch and Scott). However, the lipid content of Sertoli cells increases with age. The functional significance of this is unknown.
Spermatogenesis which occurs continuously in sexually mature males is reduced in older men, although total inability to produce sperm is rarely found even in very old men. Molnar reported that the number of sperm in the ejaculate of men in their sixties was about 30% lower than at previous ages and in much older men, this percentage decrease was even greater. Reduced spermatogenesis is thought to be related to changes in the seminiferous tubules and to decreased androgen levels. Aging males display a proliferation of connective tissue along the basement membrane of the seminiferous tubules (Engle; Molnar) which may interfere with effective sperm production. Alterations in the size and shape of sperm are more frequently seen in aging men.
Genital tract and duct systems require androgens for maintenance. Lowered androgen levels contribute to age-related changes. The seminal vesicles show weight reduction after age sixty and display decreased secretory activity. The prostate gland often follows a predictable sequence of change beginning as early as the forties and ending in the mid-fifties with muscular atrophy and fibrosis (Moore; Steward and Brandes). There often is dramatic enlargement in the seventies and eighties. This sequence of prostate changes is not inevitable but occurs with a high relative frequency in aging men. Enzyme and secretory activity of the prostate is reduced. Since the prostate contributes 20% and the seminal vesicles 60% to the total volume of seminal fluid, reduced secretory activity of these accessory structures results in lower amounts of ejaculate as well as a change in the composition of semen in older males.
There is no male analogue for female menopause, although reports of “menopausal” symptoms in middle-aged males crop up in the clinical literature from time to time. Since male reproductive capability shows only gradual changes and since there are no abrupt hormonal alterations, the analogy is a loose one at best. Benjamin has reported male patients with symptoms of irritability, insomnia, depression, and hot flashes. These symptoms tended to occur in the sixties and seventies. Other reports suggest that they may come earlier with the onset of prostate difficulties. Rubin cited a study of 273 men with menopausal complaints. In that sample, 90% complained of nervousness with a similar proportion claiming impotence. Eighty-one percent said they experienced a loss of libido, and the same percentage experienced irritability and fatigue. Libido and sexual capability, although the least frequent of female menopausal complaints, were much more common in this male sample. Lowered androgen levels may have been responsible for libidinal changes in these men. Menopausal women who experience abrupt estrogen (but not androgen) changes do not show these libidinal changes (or at least do not report them as frequently). In fact, Masters and Johnson report increases in libido in some segments of their postmenopausal sample. Since androgens underlie libido in both males and females, it is reasonable to suppose that the relatively greater androgen decline in older males (compared with older females) should lead to more pronounced libidinal changes in males. The degree to which physical condition and sexual expectations affect libido for both males and females is unknown, so libidinal changes cannot be tied solely to hormonal shifts.
Endocrine and reproductive tract changes also are accompanied by altered abilities in sexual capacity.
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