What is a TSHoma?

A TSH-secreting pituitary adenoma (TSHoma) is a rare functional pituitary tumor that produces excessive thyroid-stimulating hormone (TSH), leading to central hyperthyroidism. It accounts for less than 1% of all pituitary adenomas.

Clinical Features:

• Hyperthyroidism Symptoms: Palpitations, weight loss, heat intolerance, tremors, anxiety.
• Goiter: Diffuse thyroid enlargement is common.
• Mass Effect: Large tumors may cause visual field defects or headache.

Diagnosis:

• Elevated TSH with Elevated Free T4/T3: Key distinguishing feature from Graves' disease (where TSH is suppressed).
• MRI Pituitary: Identifies the adenoma.
• Alpha Subunit Measurement: Often elevated in TSHomas.

Treatment:

• Surgery: Transsphenoidal resection is first-line treatment.
• Somatostatin Analogues: Octreotide/Lanreotide can suppress TSH secretion and reduce tumor size.
• Radiation: For residual or refractory tumors.