[Long-term observation of serum hormone fluctuations in aging model of gonadectomized rat]

Serum LH increased rapidly in both sexes after gonadectomy, showing a peak at the 8th week. Afterwards, LH decreased gradually until the 75th week. In general, LH values in males were lower than those in females. FSH, as well as LH, increased rapidly after gonadectomy. In male serum FSH reached a peak at the 8th week and then decreased showing two peaks at the 34th and 92nd weeks. Serum FSH level decreased remarkably after the 96th week in males. In females FSH increased gradually with a subsequent rapid increase from the 28th week and reached a peak at the 42nd week. Afterwards, this FSH level was maintained to the 128th week. Serum progesterone (P4) decreased after gonadectomy in females, whereas it increased to 4 fold in males. In males this high level was maintained to the 66th week. Serum estradiol (E2) decreased in both sexes until the 3rd week after gonadectomy. However, in males the serum E2 level increased at the 4th and 5th weeks and reached the level of the 1st week after gonadectomy. Afterwards, the E2 level decreased to 10pg/ml at the 40th week which was maintained to the 128th week. In females, E2 increased from the 5th to 22nd week and decreased again from the 33rd week, and then the E2 level decreased rapidly to about 10pg/ml which was maintained to the 128th week. The present experiment indicated two results in male rats. 1. Serum FSH decreased remarkably after the 96th week of gonadectomy. 2. Serum P4 increased in spite of gonadectomy.