Serum LH, FSH, Prolactin and Progesterone from Birth to Puberty in Female and Male Rats

Serum LH, FSH, prolactin and progesterone were determined in male and female prepuberal rats. Neonates of both sexes had high LH and FSH levels, the values in the females being higher than those in the males. Serum prolactin and progesterone were low in neonatal rats. A curious LH secretion pattern occurred in female rats between days 10 and 20; high LH levels were observed in 10–15‰ of the rats during this time, whereas the male rats showed only minor fluctuations. At the same time serum FSH was elevated in both sexes. Again, the values in the females were higher than in the males. Serum prolactin was still low, whereas progesterone rose slightly in both sexes. Serum LH and FSH remained low between days 21 and the immediate peripuberal period (i.e., days 37–45) in males and females, and serum prolactin rose steadily during this period. Progesterone also increased following the prolactin pattern. All hormones (LH, FSH, prolactin and progesterone) were increased during the peripuberal period with cyclic fluctuations in the females. The close relation of prolactin and progesterone secretion in the immature rat is discussed.(Endocrinology94: 1003, 1974)