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

RINALDINI E; ELISA PIETROBON; TRONCOSO MARIANA; GAMARRA LUQUES CD,; HAPON MB

Congreso; XXXIX Reunión Científica Anual de la Sociedad de Biología de Cuyo; 2021

The endometrium plays a fundamental role in the process of implantation and nutrition of the embryo. To enable implantation, this tissueis subjected to dynamic remodeling (decidualization) under strict hormonal regulation, mainly commanded by the ovarian hormonesestradiol (E2) and progesterone (P4). During this period, E2 and P4 also contribute to the formation of new blood vessels, regulating theaction of vascular endothelial growth factor (VEGF), the main modulator of angiogenesis and vascular permeability of the decidua. Thyroidhormones (TH) play an important role during implantation and the early stages of embryonic development, being essential in maintainingthe reproductive capacity. Defects in maternal thyroid status affect the metabolism of sex steroid hormones and ovarian function that areassociated with miscarriages, placental abruption, and premature labor. Our laboratory showed that hypothyroid rats present an alteredsexual cycle, a lower number of pups per litter and a delay in the onset of parturition. Therefore, we hypothesize that THs modulate ovarianhormonal secretion and their uterine response during implantation; thus altering the correct development of the uterine decidua. The aimof this work was to investigate endometrial cell response to THs signaling, through the study of the serum concentration of the E2 and P4and the uterine expression of the receptors (ERα and PGR). In addition, the expression of TH receptor (TR) and PCNA (as an indicator ofcell proliferation) in the uterus during the implantation period was analyzed. Euthyroid (Eut) and Hypothyroid (HypoT) female Wistar ratswere 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 byimmunohistochemistry. Our results demonstrated that HipoT rats showed a significant increase in serum P4 concentration during the G7.Hypothyroidism decreased the expression of receptors for ovarian hormones, thyroid hormones and PCNA throughout the analyzedgestation period (p˂0.05). We conclude that, at uterine level, maternal thyroid status influences the adequate metabolism of the mainovarian hormones and their uterine response, affecting the decidualization process. This evidence shows the impact of THs for the processof implantation and the progression of embryo development.