Gestation and Lactation-Dependent Effects of Experimental Hyperthyroidism

Thyroid hormones (T3 and T4) play an essential role in reproductive health and can influence the functions of several endocrine and reproductive tissues, including ovaries, placenta, and mammary glands. Their interactions with other steroid hormones, such as glucocorticoids, estrogens, and progesterone, can alter the balance necessary for reproductive success. Hyperthyroidism can lead to significant endocrine dysregulation that affects multiple reproductive stages. This endocrine disorder causes several alterations in the estrous cycle, restricting conception when the condition is chronic. During pregnancy, hyperthyroidism may lead to several changes associated with preterm birth, which can adversely compromise subsequent lactation. Additionally, during lactation, excess thyroid hormones can impair both the development of the offspring and the extent of lactation by altering the mammary glands and the characteristics of the milk produced. This review explores the endocrine mechanisms behind the effects of experimental hyperthyroidism induced by T4 administration on reproduction. Furthermore, understanding iatrogenic-induced hyperthyroidism is vital for developing therapeutic strategies to mitigate its negative consequences on maternal and neonatal health.