Kinetics of Human Chorionic Gonadotropin-Induced Steroidogenic Response of the Human Testis. II. Plasma 17α-Hydroxyprogesterone, Δ⁴-Androstenedione, Estrone, and 17β-Estradiol: Evidence for the Action of Human Chorionic Gonadotropin on Intermediate Enzymes Implicated in Steroid Biosynthesis*

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).…”

“…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). The resemblance of these enzymic lesions to those observed in the mouse testis after the chronic administration of oestradiol (Samuels, Bussmann, Matsumoto & Huseby, 1964) led to the hypothesis that the rise in oestradiol after hCG stimulation was responsible for the refractory period noted in vitro (Tsuruhara et al, 1977;Forest et al, 1979;Cigorraga, Sorrell, Bator, Catt & Dufau, 1980 Sharpe & Fraser, 1980a) with 2 mg glucose/ml or buffer plus 700 mi.u./hCG ml, a dose shown previously to result in maximal stimulation (Risbridger, Robertson & de Kretser, 1982). Testes were incubated at 34°C for 4 h in a shaking water bath according to methods previously described (de Kretser, Sharpe & Swanston, 1979) Testosterone.…”

The effect of chronic treatment with GH on gonadal function in men with isolated GH deficiency

“…They suggested that this different response to CG during GH treatment was due to increased enzyme activity (31). Similarly, plasma E 2 levels were in the normal range before treatment and did not show any significant increase during treatment.…”

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).…”