Pituitary Hyperplasia Secondary to Hypothyroidism Caused by Hashimoto's Thyroiditis in a Female Adolescent

Pituitary enlargement secondary to primary hypothyroidism is a known but uncommon occurrence and is difficult to distinguish on computed tomography (CT) and magnetic resonance imaging (MRI) from primary pituitary tumor. The lack of thyroxine feedback found in uncontrolled primary hypothyroidism leads to elevated levels of thyrotropin-releasing hormone (TRH), which causes both pituitary thyrotroph and lactotroph hyperplasia, increasing the secretion of both thyroidstimulating hormone (TSH) and prolactin. With long-standing hypothyroidism, thyrotroph hyperplasia can result in expansion of the sella turcica and enlargement of the pituitary gland. Pituitary hyperplasia usually regresses following adequate treatment with hormone replacement over a period of a few months. We herein report a case of pituitary hyperplasia associated with hypothyroidism in a short statured female adolescent without the typical clinical features associated with hypothy-