LUTEINIZING-HORMONE, FOLLICLE-STIMULATING-HORMONE, TESTOSTERONE AND DIHYDROTESTOSTERONE DURING TESTICULAR DESCENT IN THE PIG FETUS

To investigate the relationship between gonadotrophins, androgens and testicular descent in the pig fetus, serum concentrations of luteinizi ng hormone (LH) and follicle-stimulating hormone (FSH), and serum conc entrations and testicular content of testosterone (T) and 5 alpha-dihy drotestosterone (DHT) were determined by radioimmunoassay in 95 fetuse s (48 males, 47 females) between Day 60 and Day 90 post coitum (p.c.). The testes were descended in 0% of fetuses at Day 60, 8% of fetuses a t Day 70, 40% of fetuses at Day 80 and 87% of fetuses at Day 90 p.c. T here was a significant increase in mean serum concentrations of LH in both male and female fetuses from Day 60 to Day 80, with a significant difference in mean serum concentrations of LH between male fetuses wi th a body mass <350 g (4% of testes descended) and those with a body m ass >450 g (87% of testes descended), but not between male and female fetuses <350 g or >450 g in body mass. There was no significant differ ence in mean serum concentrations of FSH between male and female fetus es. Mean serum concentrations of T were significantly higher in male f etuses at Day 60 than in those at Days 70-90, with no significant diff erence in serum concentrations of DHT from Day 60 to Day 90 p.c. Testi cular content of T and DHT showed a non-linear increase from Day 60 to Day 90 p.c. Although the serum concentration of T is elevated before, and decreased during, the period of descent, the testicular content o f T and DHT increases during the period of descent, indicating that se rum concentrations of LH and FSH may have an indirect effect on descen t by stimulating testicular androgen synthesis.