ROLE OF THYROID HORMONES IN THE UTERINE RESPONSE TO OVARIAN HORMONES AND DECIDUAL PROLIFERATION

RINALDINI, E; PIETROBON, E.; TRONCOSO M.; GAMARRA LUQUES, C; HAPON, MB

SAN LUIS

Congreso; XXXIV Reunión Científica Anual de la Sociedad de Biología de Cuyo.; 2021

Sociedad de Biología de Cuyo

The endometrium plays a fundamental role in the process of implantation and nutrition of the embryo. To enable implantation, this tissue is subjected to dynamic remodeling (decidualization) under strict hormonal regulation, mainly commanded by the ovarian hormones estradiol (E2) and progesterone (P4). During this period, E2 and P4 also contribute to the formation of new blood vessels, regulating the action of vascular endothelial growth factor (VEGF), the main modulator of angiogenesis and vascular permeability of the decidua. Thyroid hormones (TH) play an important role during implantation and the early stages of embryonic development, being essential in maintaining reproductive capacity. Defects in maternal thyroid status affect the metabolism of sex steroid hormones and ovarian function that are associated with miscarriages, placental abruption, and premature labor. Our laboratory showed that hypothyroid rats present an altered sexual cycle, lower number of pups per litter, and delay in the onset of parturition. Therefore, we hypothesize that THs modulate ovarian hormonal secretion and their uterine response during implantation; thus altering the correct development of the uterine decidua. The aim of this work was to investigate endometrial cell response to THs signaling, through the study of the serum concentration of the E2 and P4 and the uterine expression of the receptors (ERα and PGR). In addition, the expression of TH receptor (TR) and PCNA (as an indicator of cell proliferation) in the uterus during the implantation period was analyzed. Euthyroid (Eut) and Hypothyroid (HypoT) female Wistar rats were used. Hypothyroidism was induced by daily administration of the antithyroid 6-propyl-2-thiouracil (PTU) 0.1 g/L in drinking water, while the control group only drank tap water. Groups of 6-7 rats were sacrificed on days five (G5), six (G6) and seven (G7) of gestation. Hormones were measured by radioimmunoassay and the expression of uterine ERα, PGR, TR and PCNA were evaluated by immunohistochemistry. Our results demonstrated that HipoT rats showed a significant increase in serum P4 concentration during the G7. Hypothyroidism also decreased the expression of receptors for ovarian hormones, thyroid hormones and PCNA throughout the analyzed gestation period (p˂0.05). We conclude that, at uterine level, maternal thyroid status influences the adequate metabolism of the main ovarian hormones and their uterine response, affecting the decidualization process. This evidence the impact of THs for the process of implantation and the progression of embryo development.