A Narrative Review on the Effect of Maternal Hypothyroidism on Fetal Development

The thyroid is a butterfly-shaped gland located in the human body's neck region. The thyroid produces three hormones that are essential for regulating body temperature, energy production, weight, hair and nail growth, and menstrual cycle maintenance. The production of these hormones is controlled by a feedback mechanism. Various factors cause changes in the stimulation and inhibition of these hormones, which ultimately causes either excessive release or a decrease in the levels of thyroid hormones. These causes can be physiological or pathological. One of the physiological causes is pregnancy. Pregnancy is a very complex process in which many changes occur in the body and its functioning. One of which is changes in the maternal thyroid gland. The inability to adequately adapt to the changes leads to the abnormal functioning of the thyroid gland. During pregnancy, there is a variation in the concentration of thyroid hormones which may cause a decrease in levels or inhibition in the production of thyroid hormones. This condition is called hypothyroidism. Hypothyroidism in pregnant mothers can either be gestational or may be a condition that is present way before her pregnancy. Often, gestational hypothyroidism reverts after delivery during the postpartum period but can also be present as subclinical hypothyroidism. In such cases, they pose a significant threat to development, cause growth hindrance to the infant in the womb, and cause abnormalities in the offspring in the future. Some of the changes occur in the gland because of enhancement in levels of thyroid binding globulin, increased clearance rate of iodine from the body in kidneys, altered effects in human chorionic gonadotropin hormone, and decreased consumption of iodine in meals. Iodine disbalance in maternal hypothyroidism is associated with severe health issues like cretinism and mental retardation. Thyroid hormones are crucial for the infant's neural, cognitive, and intelligence quotient development in the womb. Thus, the disturbances in the maternal hormone levels disturb typical early developmental characteristics. In the world of rapidly advancing scientific research, there are many ways in which this condition can be detected early, diagnosed correctly, and given apt and required attention and treatment for causing the least harm to the fetus and the mother.