Leydig Cell Responsiveness to Single and Repeated Human Chorionic Gonadotropin Administration

Abstract

A single im injection of 1500 IU hCG significantly increased plasma testosterone levels for at least 96--120 h in normal men (n = 7), patients with isolated gonadotropin deficiency (n = 6), and boys with delayed puberty (n = 7); the maximum values [1315 +/- 309, 370 +/- 177, and 963 +/- 249 ng/100 ml (mean +/- SD), respectively] were achieved after 72 h in each group. Repeated daily injections of 1500 IU hCG for 3 days increased plasma testosterone levels in the same subjects at 72 h after the start to levels (1342 +/- 412, 407 +/- 199, and 1052 +/- 449 ng/100 ml, respectively) similar to those found in the single dose experiment. The levels achieved at 24 and 48 h also did not differ significantly in the two experiments. The data indicate the lack of additional leydig cell stimulation by repeated hCG injections given within 48 h after a single dose.

Effect of oestradiol and tamoxifen on the testosterone response in male rats to a single injection of hCG

“…In confirmation of this view, a second injection of hCG was ineffective in modifying testosterone levels for approximately 3 days . Equivalent studies in man have also indicated an in-vivo refractoriness, since quantitatively similar testosterone responses were observed after single and 3 daily injections of hCG (Smals, Pieters, Drayer, Benraad & Kloppenborg, 1979 showed an increase in progesterone and 17a-hydroxyprogesterone concomitant with the falling concentration of testosterone between 2 h and 3 days, indicating a lesion in the steroidogenic pathway at the 17a-hydroxylase and C17_2o lyase enzymes (Forest, Lecoq & Saez, 1979). Similar lesions have been reported for suspensions of purified rat Leydig cells 2 and 3 days after hCG treatment (Tsuruhara, Dufau, Cigorraga & Catt, 1977;Cigorraga, Dufau & Catt, 1978).…”

Kinetics of the Steroidogenic Response to Single versus Repeated Doses of Human Chorionic Gonadotropin in Boys in Prepuberty and Early Puberty

“…In pubertal boys estradiol levels increased progressively throughout the stimulation. The major testosterone response was seen after the first dose of hCG and repeated doses, at least in the pubertal boys, increased estradiol but not testosterone levels, thus causing an estrogen-mediated 17,20- Excessive amounts of gonadotropins are known to desensitize steroidogenesis in the rat and in adult men (5,6,8,10,15,16,22). This is a complex process which includes a decrease in the activities of l7a-hydroxylase and 17,20-lyase enzymes and an accumulation of steroid intermediates, such as progesterone and 170HP (6,8,15).…”

Evaluation of endocrine testing of Leydig cell function using extractive and recombinant human chorionic gonadotropin and different doses of recombinant human LH in normal men

“…Furthermore, a gonadotropininduced activation of Leydig cell aromatase leads to a rise in E 2 synthesis (14,17,23). Multiple injections of ehCG give similar results as a single one (16,24,25). A prolonged exposure to elevated doses of hCG induces a desensitization process in rat and man (22,26,27).…”

“…The effects of an acute injection of ehCG on the yield of T and E 2 are well demonstrated in animal and man (16,17,21). In normal adult men, plasma E 2 and T levels reach a peak 24 and 72 h respectively after a single i.m.…”

“…On the other hand, hCG testing of Leydig cell function was of interest for the search of the presence of intra-abdominal testes in case of bilateral ectopia (6,7), for differentiating delayed puberty from hypogonadotropic hypogonadism (11)(12)(13), and for the etiological diagnosis of gynecomastia (14,15). Various modalities of testing have been proposed in terms of hCG doses, the number of injections, and times of blood drawing (3,11,13,16). The widely used hCG testing of Leydig cell function in adulthood is performed with one injection of 5000 IU hCG and measurements of plasma T and E 2 before and every morning of the 3 days following the injection (12,(17)(18)(19).…”