During early pregnancy, what hormone stimulates the thyroid, leading to increased levels of free thyroid hormones?

During early pregnancy, human chorionic gonadotropin (hCG) plays a crucial role in stimulating the thyroid gland, which subsequently leads to increased levels of free thyroid hormones. hCG is produced by the placenta soon after conception and is structurally similar to thyroid-stimulating hormone (TSH). This similarity allows hCG to bind to TSH receptors on the thyroid gland, stimulating it to produce more thyroid hormones, which are essential for both maternal metabolism and fetal development.

Increased levels of free thyroid hormones are vital during early pregnancy, as they support various physiological processes, including growth and development of the fetus, as well as maternal metabolic needs. Consequently, the ability of hCG to mimic TSH and stimulate thyroid activity is significant in maintaining the necessary hormonal balance.

The other choices represent hormones that do not have this specific role in early pregnancy. Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) are primarily involved in the regulation of the menstrual cycle and ovulation, and do not directly stimulate the thyroid. Thyroid-stimulating hormone (TSH) is indeed important for regulating thyroid function but is not the hormone that initiates this action during the early stages of pregnancy, as hCG takes