Follicular development and ovulation in hypothyroid rdw rats

In this paper, we summarized our recent studies on follicular development a nd ovulation in the presence or absence of thyroxine (T4) and equine chorio nic gonadotrophin (eCG) treatment in infertile immature spontaneously hypot hyroid rdw rats. T4 therapy once daily from postnatal day 21 to day 29 resu lted in increases in ovarian weight on day 30 (P 0.01). Similar populations of both healthy and atretic antral follicles ranging in diameter from 101- 400 tm were observed in control rdw and normal rats. T4 treatment markedly increased the numbers of healthy antral follicles of 101-400 mum or larger than 550 mum in diameter in the absence or presence of eCG, respectively, i n rdw rats. On the other hand, T4 treatment did not affect the population o f atretic antral follicles, but decreased the number of atretic large antra l follicles (> 400 mum) in the presence of eCG. Although a few (5 +/- 2) eg gs were obtained from immature rdw rats treated with gonadotrophins alone, significantly more eggs (85 +/- 5) were ovulated from females treated with gonadotrophins and T4. As a control, normal littermates ovulated 45 eggs wh en treated with gonadotrophins only and 68 eggs when to them were also give n T4. In conclusion, the results of the present study indicated that T4 tre atment improved follicular development in the presence of eCG and significa ntly increased the number of ovulated eggs following hCG treatment in rdw r ats.