Early effects of hypothyroidism on the ovarian function in the rat.

HAPON MB,; BUZZIO OL,; GAMARRA LUQUES CD,; JAHN GA.

Vancouver , British Columbia, Canada

Congreso; 37 th Annual Meeting of the Society for the Study of Reproduction; 2004

Society for the Study of Reproduction

Hypothyroidism (hypoT) in the female is associated with delayed puberty, menstrual abnormalities, PCOS, infertility and spontaneous abortion. We have observed previously that hypoT female rats have irregular estrous cycles, spontaneous pseudopregnancies(Psp) and smaller litters. IGF I and some of its binding proteins (BPs) are produced locally in the ovary, IGFI is involved in FSH and GH stimulated preovulatory follicular development and IGFBP 3,4 and 5 regulate de action of IGFI. The expression of the IGF system is modified in altered thyroid state. To explore the early effects of hypoT on ovarian function we studied the effects of PTU 0.01 % in the drinking water given to 3-4 months old female virgin rats, on cycling, reproductive hormone profie (T3,T4, TSH, PRL, GH, E2, and P4) measured by RIA, and the abundance of mRNA (measured by semiquantitative RT-PCR and expressed relative to S16) for IGFI, IGFBP3 and 5, and GH (GHR), estrogen (ER) and PRL (PRLR) receptors, during the 2nd cycle after the initiation of PTU treatment. Measurements were taken at 20 h on all days of the cycle an also at 08 h on proestrus (P) and estrus (E). The PTU rats showed increased TSH and decreased T3 and T4 . Ovulation rate and circulating P4, LH and FSH presented no changes between groups. But PRL and E2 increased on E8 h and 20 h an GH decreased on P8h. Expression of IGFI did not change IGFBP3 fell in the hypoT group on diestrus (D) 1 and 2 and rose at P08 h, and IGFBP5 fell on D1. PRLR decreased on D1, GHR increased at P20 hs. ERa decreased at P 20 h and increased at E8 h and ERb increased a P20 and E20h. The increased GHR mRNA n P may have compensated the lower secretion of GH in P8h in the hypoT group. The increases in circulating PRL, and E2, may be responsible for the posterior apparition of spontaneous Psps. The changes observed in the ovarian gene expression were not sufficient to induce alterations in the sududied cycle, but may play a role in the posterior ovarian dysfunctions and establishment of PCOS observed in HypoT rats.