Responsiveness of the Pituitary-Testicular Axis to Gonadotropin-releasing Hormone and Chorionic Gonadotropin during the First Week of Life

Abstract

ABSTRACT. Qualitative changes are known to occur in testicular steroidogenesis at birth as the testosterone peak is reached without significant elevation of basal luteinizing hormone in the 2nd wk of life. This study was designed to evaluate testicular activity prior to these changes. Pituitary-testicular function was studied by measuring serum gonadotropins and steroids after stimulation by gonadotropin-releasing hormone (GnRH) (one intravenous injection) and human chorionic gonadotropin (hCG) (three intramuscular injections). The subjects had minor genital anomalies; their ages ranged from 2 to 6 days. All had a strong luteinizing hormone response and a weaker follicle-stimulating hormone response to GnRH stimulation. hCG induced significant increases in serum pregnenolone, 17-hydroxyprogesterone, androstenedione, testosterone, and dihydrotestosterone. Serum estradiol and estrone did not change, and progesterone decreased. The results clearly show that the pituitary-testicular axis is functional neonatally. The responsiveness of the testis to hCG supports the assumption that the postnatal decrease of testicular steroids is due to the simultaneous disappearance of hCG from the circulation. Ez, estradiolIn male infants, the relatively high concentrations of serum testosterone found on the 1st postnatal day decrease rapidly to a low level which is maintained for about 1 wk, after which a transient activation of the hypothalamic-pituitary-testicular axis Received November 28, 1983; accepted March 23, 1984 takes place (4, 12, 1 3, 16). During the period of relative testicular quiescence on days 3 to 6 after birth, stimulation by GnRH evokes significant response in serum LH concentrations (14). It has not been knbwn to date whether the testis could respond to LH or hCG stimulation in this period. The aim of this study was to test this as such information would be of value in understanding the regulation of testicular function. As such studies cannot be made in normal human newborns we chose those with only minor genital anomalies as subjects. They were given a GnRH test followed by a hCG test. MATERIALS AND METHODS Subjects.Our series consisted of 16 full-term newborn male infants with minor genital abnormalities. They were 2.25 to 6.0 days old at the beginning of the testing. Twelve had incomplete testicular descent; nine unilaterally (four testes were not palpable) and three bilaterally (all inguinal). Only one infant had a testis still not palpable at the age of 12 months but at surgery, it was found to be of normal size and consistency. Three of the other infants needed an orchidopexy at the age of 1 yr. Two infants had surgically insignificant glandular hypospadias and two had a penis shorter than mean -2SD for gestational age (2). The Ethical Committee of the Hospital approved this study, and an informed consent was obtained from all parents.Tests. To the release of the pituitary gonadotropins, GnRH (Relefact, Hoechst AG, F. R. G.), 3.5 pg/kg was injected intravenously during 1 min between 0830 and 1100. One-...

Serum levels of sex hormone‐binding globulin (SHBG) are not associated with lower levels of non‐SHBG‐bound testosterone in male newborns and healthy adult men

“…The absent relation between SHBG and non‐SHBG‐T in our subjects implies that the observed testosterone levels are not just the result of an unleashed HPG axis but are restrained by the feedback inhibition of non‐SHBG‐T. This is supported by the observation that LH and/or testosterone secretion in neonates can be further increased when stimulated with GnRH or human chorionic gonadotropin 19 . Although the HPG axis is operative in neonates, circulating (non‐SHBG) T levels are much lower than in adults.…”

“…This is supported by the observation that LH and/or testosterone secretion in neonates can be further increased when stimulated with GnRH or human chorionic gonadotropin. 19 Although the HPG axis is operative in neonates, circulating (non-SHBG) T levels are much lower than in adults. It appears that the higher SHBG levels found in neonates are not responsible for the relatively low levels of non-SHBG-T. A different setpoint of the HPG axis in neonates might thus be postulated.…”

Smith-Lemli-Opitz syndrome: in vivo and in vitro study of testicular function in a prepubertal patient with ambiguous genitalia

“…Low testosterone production and poor response to stimulation with hCG had already been reported in SLOS (15). This is not expected, since it has been reported that positive response to hCG stimulation is found in normal prepubertal boys at any age (10), including the first week of life (16). The histology of the testes was normal for age, and there was no evidence of testicular dysgenesis.…”