Thyrotoxic periodic paralysis as the first manifestation of a thyrotropin-secreting pituitary adenoma.

Thyrotoxic Periodic Paralysis (TPP) is a rare manifestation of hyperthyroidism characterized by muscle weakness and hypokalemia. Thyroid-Stimulating Hormone (TSH)-secreting pituitary adenoma is a rare cause of hyperthyroidism. Even more rare is the occurrence of TPP as the first manifestation of a TSH-secreting pituitary adenoma. We report a 31-year-old Asian male patient suffering from TPP caused by a TSH-secreting adenoma, who was evaluated for persistent episodes of muscle paralysis. Laboratory investigation revealed hypokalemia as well as elevated levels of both thyroid hormones and TSH. The Magnetic Resonance Imaging (MRI) of the pituitary gland revealed a microadenoma, thus suggesting the presence of a TSH-secreting adenoma. The patient underwent transphenoidal resection and the pathological investigation confirmed the diagnosis of TSH-secreting pituitary adenoma. After the adenomectomy and the restoration of euthyroidism, the patient did not experience any episode of hypokalemic paralysis or weakness. Despite its rarity, TSH-secreting pituitary adenoma should be included in the differential diagnosis of TPP.