The pituitary-gonadal axis in the female child during infancy and at puberty

Abstract

Serum FSH and LH (radioimmunoassay), estradio (radioimmunoassay, and testosterone (competitive protein-binding) were studied in 120 healthy females aged 0–20 years, and correlated with physical development. Prepubertal girls (4–9 years) showed low levels of FSH (6–12 μg LER-907%), LH (0.5–2.5 μg%), estradiol (<I ng%) and testosterone (<20 ng%). Puberty (thelarche and pubarche) was accompanied by a rise in all these variables, reaching adult levels by age 14–16. The earliest hormonal change (age 9–11) was a rise in serum FSH, together with estradio and testosterone; serum LH rose later (around age 12). These data resemble our previous findings in male. In 0–2 year old females, serum FSH (8–40 μg%) and LH (1.3–3.0 μg%) levels were higher than those in male infants (FSH 4–10 μg%, p < .01; LH 0.5–2.0 μg%, p < .01). Female FSH and LH levels diminished from age 0–8 years, while in boys these values increased slightly during this time. Estradiol and testosterone levels were not elevated in infancy. Serial determinations of FSH and LH in infant chimpanzees demonstrated similar constant low values (FSH 5–9 μg%, LH 2.2–3.1 μg%) in males; female chimps had higher values (FSH 13–40 μg%, LH 2.2–6.1 μg%). Moreover the females sowed day-to-day cyclicity of varying amplitude (with 6–14 day periodicity). This sex difference in hypothalamo-pituitary function in infancy possibly represents an effect of differing intra-uterine exposure to endogenous androgen. This is the first demonstration of an endocrine sex difference in primates prior to puberty.