Age-related changes in the concentrations of serum gonadotrophins and cholesterol in the female rabbit

Peripheral serum concentrations of LH, FSH and prolactin were determined by radioimmunoassay on different days after birth in the female rabbit. Serum cholesterol concentrations were also analysed by a colorimetric method. Concentrations of serum LH and FSH showed two distinct peaks occurring on day 9 (LH, 4.05 +/- 0.76 (mean +/- S.E.M.) micrograms/l; FSH, 3.62 +/- 0.67 microgram/l) and either day 35 (LH, 5.90 +/- 1.20 micrograms/l) or day 40 (FSH, 9.01 +/- 1.43 micrograms/l). Concentrations of LH and FSH were in the adult range (LH, less than 1 microgram/l; FSH, less than 0.6 micrograms/l) by day 100. Serum prolactin showed a progressive increase from day 1 (1.04 +/- 0.07 microgram/l) to day 100 (17.30 +/- 2.50 micrograms/l) with a peak on day 40. Total serum cholesterol in another series of rabbits was high from days 1 to 22 (7.53 +/- 0.64 mmol/l) and then decreased to 1.94-3.36 mmol/l by day 106. These data indicate that the two major developmental peaks in gonadotrophins may be related to ovarian function.