Hyperprolactinemia is a common finding in primary hypothyroidism, but increased prolactin in the setting of subclinical hypothyroidism (SCH) has been scarcely reported in the literature. This is a rare case of hyperprolactinemia due to SCH that resolved with thyroid hormone replacement therapy. The patient was not on any medications known to cause hyperprolactinemia but she was using isoniazid for her latent tuberculosis. Isoniazid therapy may explain breast pain, but there is no reported relationship between isoniazid use causing subclinical hypothyroidism and hyperprolactinemia. A literature review reveals that few cases of galactorrhea associated with subclinical hypothyroidism have been reported. Similar to the reported cases in the literature, our patient's thyroid stimulating hormone (TSH) and prolactin levels returned to normal with levothyroxine therapy.
Keywords: galactorrhea; hyperprolactinemia; levothyroxine; primary hypothyroidism; subclinical hypothyroidism.