Thyroid hormone affects rat uterine expression of IGF-I and IGFBP-4

The rat uterus has been shown to be a site of production of insulin-like growth factor-I (IGF-I) and multiple IGF-binding proteins (IGFBP-2, -3, -4, -5, -6) which are involved in estrogen-induced uterine proliferation. The presence of T3-receptors in rat uterus suggests a role of thyroid hormone in the regulation of uterus responses to estradiol. In this study IGF-I and IGFBP-4 mRNAs in uterus, oviduct and cervix from euthyroid, hypothyroid and T3-treated rats were quantified by Northern blot analysis. Our results demonstrate: i) a marked decrease in IGF-I and IGFBP-4 mRNA levels in the uterus but an increase in the oviduct of hypothyroid rats; ii) a marked increase in IGF-I and IGFBP-4 mRNA levels in the uterus but a net decrease in the cervix of T3-treated rats. The uterine changes in IGF-I and IGFBP-4 mRNA levels associated with hypothyroid status were in agreement with those observed in liver.