In hypothyroidism, the thyroid fails to produce sufficient thyroid hormones, and the levels of thyroxine (T4) and sometimes triiodothyronine (T3) are too low. Because of this, the body’s feedback mechanisms try to stimulate the thyroid gland by producing more thyrotropin-releasing hormone (TRH). TRH triggers the release of thyroid-stimulating hormone (TSH) from the anterior pituitary gland. The action of TRH on the anterior pituitary gland also triggers the release of more prolactin, so prolactin levels increase with TRH levels and TSH levels in hypothyroidism. This does not happen in every case of hypothyroidism; however, it is worth testing for hypothyroidism as a possible cause of hyperprolactinemia.[1][2]
Why does hypothyroidism cause hyperprolactinemia?
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•Last Updated: May 16, 2025
In hypothyroidism, low thyroid hormone levels trigger the release of thyrotropin-releasing hormone, which stimulates the release of thyroid-stimulating hormone (TSH) and prolactin from the anterior pituitary gland. This can cause elevated levels of prolactin, which results in hyperprolactinemia.