Circulating Concentrations of FSH, LH, Estradiol, and Progesterone Associated with Acute, Male-Induced Puberty in Female Mice

Abstract

Changes in circulating concentrations of pituitary gonadotropins and ovarian steroids were examined in young female mice undergoing male-induced, precocial puberty. Preliminary experiments revealed that body weight was the most critical factor in determining the rapidity with which puberty could be so induced. A restricted (lg) weight range, at which 80–85% of the immature females would uniformly achieve a complete ovulatory cycle in a 3-day period, was thus chosen as a model system for studying hormonal changes. Under these predictable conditions, male exposure was followed by a 4–5-fold increase in serum LH in 1–3 hr, and a 15–20-fold increase in plasma es-tradiol in 3–6 hr. Circulating concentrations of FSH and progesterone did not change during the first 24 hr of male exposure. A second peak in plasma estradiol levels was detected during the second day. FSH, but not LH, was totally depressed at this time. Normal, adult-like, periovulatory changes in serum LH and FSH and in plasma progesterone (but not estradiol) began late in the afternoon of the third day. It is postulated that the observed delay between peak circulating levels of estradiol and the ovulatory flush of LH reflects the final maturation of the positive feedback system. A final study revealed that the initial (1–12 hr), sequential changes in LH and estradiol were not in themselves sufficient to ensure completion of a pubertal cycle in the 3-day experimental period; 36–48 hr of male exposure were necessary to accomplish this. (Endocrinology94: 1658, 1974)