TSH-induced hyperthyroidism caused by a pituitary tumor

BACKGROUND: A 45-year-old man presented with frontal headache and visual disturbances to our clinic. For the previous 5 years, he had been receiving treatment for long-lasting mild hyperthyroidism with antithyroid therapy, but therapy had not been carefully followed. During the last 2 years he had also complained of erectile dysfunction and loss of libido. On physical examination, he had a small goiter, normal skin, no Graves' ophthalmopathy, normal BMI, and reduced testis volume and pubic hair. INVESTIGATIONS: Serum levels of free T3 and T4, serum prolactin, testosterone, serum gonadotropins, insulin-like growth factor 1, adrenocorticotropic hormone, and cortisol were measured. MRI scan, TSH-releasing hormone test, and T3 suppression test were carried out. Levels of pituitary glycoprotein hormone alpha-subunit and sex-hormone-binding protein were also measured. DIAGNOSIS: Hyperthyroidism caused by a mixed pituitary adenoma that secretes prolactin and TSH. MANAGEMENT: Trans-sphenoidal resection of the pituitary tumor. After surgery, T3 suppression test failed to completely suppress TSH secretion, which suggested a persistence of residual adenomatous cells. Hyperthyroidism and hypogonadism recurred after 5 years, therefore, treatment with lanreotide was initiated, and resulted in complete resolution of signs and symptoms of the disease.