Effects of Thyroid Dysfunction on Reproductive Hormones in Female Rats

Abstract

Thyroid hormones (THs) play a critical role in the development of ovarian cells. Although the effects of THs on female reproduction are of great interest, the mechanism remains unclear. We investigated the effects of TH dysregulation on reproductive hormones in rats. Propylthiouracil (PTU) and L-thyroxine were administered to rats to induce hypo- and hyperthyroidism, respectively, and the reproductive hormone profiles were analyzed by radioimmunoassay (RIA). Ovarian histology was evaluated with hematoxylin and eosin (H&E) staining, and gene protein level or mRNA content was analyzed by western blotting or reverse transcription polymerase chain reaction (RT-PCR). The serum levels of gonadotropin releasing hormone (GnRH) and follicle stimulating hormone (FSH) in both rat models were significantly decreased on day 21, although there were no significant changes at earlier time points. There were no significant differences in luteinizing hormone (LH) or progesterone (P4) levels between the treatment and the control groups. Both PTU and L-thyroxine treatments downregulated estradiol (E2) concentrations; however, the serum testosterone (T) level was increased only in hypothyroid rats at day 21. In addition, the expression levels of FSH receptor, cholesterol side-chain cleavage enzyme (P450scc), and steroidogenic acute regulatory protein (StAR) were decreased in both rat models. Moreover, the onset of puberty was significantly delayed in the hypothyroid group. These results provide evidence that TH dysregulation alters reproductive hormone profiles, and that the initiation of the estrous cycle is postponed in hypothyroidism.

Investigation of Thyroids Dysfunction Among Infertile Women in Nasiriyah City

“…These results were in agreement with many studies, showed that serum prolactin was significantly (P<0.05) higher in infertile group with thyroid dysfunction compared with control [9,20,34].…”

“…These data in agreement with Liu et al, who found that the serum levels of gonadotropin releasing hormone (GnRH) and follicle stimulating hormone (FSH) in both hypo-and hyperthyroidism rat models were significantly decreased on the luteal phase, although there were no significant changes at earlier time points. There were no significant differences in luteinizing hormone (LH) or progesterone levels between the treatment and the control groups [9].…”

“…Hyperprolactinemia was depicted in 41% of the infertile women while it was only 15% in the control group. The infertile women with hypothyroidism had significantly higher prolactin levels when compared to the subjects with hyper-or euthyroidism [9,20].…”

“…Treatment of thyroid disorders, and maintaining of the thyroidstimulating hormone level at the normal level, improved conception rates and reduce early pregnancy loss [3,8]. Thyroid dysfunction can affected female fertility from different ways included hormonal effect [9][10][11][12], abnormalities of menstrual cycle [13][14][15][16][17], effect on ovary function and ovulation [15,[18][19][20][21][22] and adverse effects on pregnancy [15,19,[23][24][25][26]. The current study aims to explore the thyroid dysfunction among infertile women.…”

The Interplay Between Hyperthyroidism and Ovarian Cytoarchitecture in Albino Rats

“…In recent times, multiple studies have been conducted to observe the effect of thyroid dysfunction on the reproductive system [ 18 ]. This study was designed to observe the effect of experimentally induced hyperthyroid state on ovarian parameters and hypophyseal-gonadal axis, in adult Wistar albino rats.…”