Changes in the Pituitary‐testicular System With Age

Abstract

In order to provide a comprehensive account of pituitary-testicular function in man, 466 subjects, ranging in age from 2 to 101 years, were studied to examine blood levels of the pituitary gonadotrophins (LH and FSH), the sex steroids testosterone and oestradiol, the binding capacity of the sex hormone binding globulin (SHBG), the free testosterone and oestradiol fractions, and the transfer constant for the peripheral conversion of testosterone to oestradiol. The results were compared with clinical indices of testicular size, sexual function and secondary sex hair distribution. Serum LH and FSH were low before puberty, increased in pubertal adolescents to levels somewhat above those of adults and subsequently increased progressively over the age of 40 years. Testosterone levels fell slowly after the age of 40, while there was a slight rise in plasma oestradiol with increasing age. FSH and testosterone showed small seasonal variations in young adult men, the lowest values being seen in winter. SHBG binding capacity was high in two prepubertal boys, fell in adult men, but increased in old age. Free testosterone and oestradiol levels fell in old age. The metabolic clearance rates (MCR) of testosterone and oestradiol also fell in old age, while the conversion of testosterone to oestradiol was increased. Many correlations were observed between various hormonal and clincial measurements. The evidence is consistent with a primary decrease in testicular function over the age of 40 years.

Endogenous sex hormones in men aged 40-80 years

“…Until recently little attention has been paid to the role of estrogens in elderly men. The studies which have been reported so far show no change of total E 2 levels with age in men (1, 9, 28), or a decrease of E 2 levels only in old age (29,30). In the present study no changes with age were found.…”

Reproductive ecology and life history of the human male

“…Similar declines were noted in salivary testosterone measurements (Read et al, 1981). Slight elevations in FSH and LH levels also suggest some degree of age-related testicular insensitivity (Baker et al, 1976;Gray et al, 1991). Older males also lose diurnal patterns of testosterone secretion that are common in younger men (Bremner et al, 1983), although the physiological significance is unknown.…”

Impact of Aging on Steroid Hormone Biosynthesis and Secretion

“…In contrast to these findings, Sniffen, [139], as well as Sokal [140] observed no loss of Leydig cells with age, while Kothari and Gupta [141] reported total Leydig cell mass to be increased in testes from their older men. Besides, a number of studies have also shown impaired testicular responsiveness to hCG stimulation [103,104,133,[143][144][145][146] or to recombinant human LH [147,148] stimulation in aging men. Harman and Tsitouras [103], Nieschlag et al, [104], Rubens et al, [144], Nieschlag et al, [142], and Nankin et al, [146] all noted decreases in both the absolute and relative (i.e., ratio of stimulated to basal) testosterone responsiveness in elderly as compared to young men.…”