Influence of thyroid hormone on mouse preantral follicle development in vitro

Objective: To evaluate the role of 3,3',5-triiodothyronine (T-3) on ovarian follicle development in vitro. Design: Experimental study. Setting: University reproductive biology unit. Animal(s): CD1 mice (female). Intervention(s): In vitro culture. Main Outcome Measure(s): Assessment of follicle and oocyte development following a 6-day culture with FSH (100 mU/mL), (Bu)(2)cAMP (0.5 mM), and T-3 (1-100 nM), alone or in combination. Result(s): A high percentage of in vitro grown (IVG) FSH-stimulated follicles formed an antral cavity (AC) while the addition of T-3 (100 nM) significantly reduced this response in a statistically significant manner. A statistically significant recovery of AC formation was obtained by limiting exposure to 4 days of culture. Formation of AC was induced by (Bu)(2)cAMP, which prevented T-3-mediated suppression of AC formation. Under different conditions, high proportions of germinal vesicle-arrested IVG oocytes displayed condensed chromatin configuration. The capacity to undergo germinal vesicle breakdown (GVBD) was similar in all groups, and a statistically significant reduction in the percentage of oocytes with PB1 was recorded when T-3 was added to FSH or (Bu)(2)cAMP. This ability was partially recovered by removing T-3 on day 4 of culture. Conclusion(s): Exposure to high T-3 concentrations can impair preantral follicle development, but this effect can be partly reverted by restoring a physiological hormonal milieu before follicle commitment to antral development. ((C) 2004 by American Society for Reproductive Medicine).