The Estrous Cycle in Female Rats Under Conditions of Experimental Hypothyroidis

The article presents the results of an experimental study aimed at investigating changes in the estrous cycle of female rats following partial thyroidectomy. The goal of modeling hypothyroidism by removing half of the thyroid gland was to examine the mechanisms through which thyroid dysfunction affects the reproductive system. Following surgery, a statistically significant increase in thyroid-stimulating hormone (TSH) levels was observed in the animals, confirming the development of hypothyroidism.An analysis of estrous cycle dynamics revealed significant alterations: the overall duration of the cycle was markedly prolonged due to an extended diestrus phase, indicating a delay or absence of ovulation. The frequency of estrus in hypothyroid females was significantly reduced, pointing to a decrease in reproductive activity. Persistent anovulatory cycles were identified, which are considered a prerequisite for infertility.Possible pathophysiological mechanisms of this phenomenon are discussed, including the impact of reduced thyroid hormone levels on the hypothalamic–pituitary–gonadal axis, altered sensitivity of gonadotropin receptors, and disruption of sex hormone balance.Particular attention is given to the role of thyroid hormones in maintaining normal ovarian function and ensuring ovulatory processes. The findings have practical significance for understanding the pathogenesis of fertility disorders associated with hypothyroidism and may be applied to improve approaches to the diagnosis and treatment of endocrine-related infertility.Thus, the study highlights the importance of regular monitoring of thyroid gland function in women of reproductive age to prevent potential reproductive complications.