Primary hypothyroidism presenting as a pituitary mass

Pituitary enlargement secondary to primary hypothyroidism is a known but uncommon occurrence, which can be difficult to distinguish on computerized tomography (CT) and magnetic resonance imaging (MRI) from primary pituitary tumors. We describe a 33 year old female who was referred to a neurosurgeon for removal of a pituitary mass. The markedly elevated thyrotrophin stimulating hormone (TSH), absence of clinical features of hyperthyroidism, and low thyroid hormone values led to a diagnosis of pituitary enlargement secondary to primary hypothyroidism. The pituitary gland returned to normal size with thyroxine replacement therapy. Surgery was not indicated.