Pituitary hyperplasia mimicking thyrotropin-producing pituitary adenoma in the patient with resistance to thyroid hormone: a case report

Abstract

The syndrome of inappropriate thyroid-stimulating hormone (TSH) secretion is characterized by high circulating thyroid hormone concentrations in the presence of non-suppressed TSH. After exclusion of the laboratory interference, TSH-secreting pituitary adenoma (TSHoma) or resistance to thyroid hormone-beta (RTH-β) should be suspected. The presence of a pituitary adenoma on the hypothalamic-pituitary imaging supports the diagnosis of TSHoma. However, the incidental findings of non-functioning pituitary adenomas may appear in patients with RTH-β. Abnormal MRI finding in the RTH-β patient also includes pituitary enlargement from thyrotroph hyperplasia. We herein reported a patient with inappropriate TSH secretion who has pituitary hyperplasia mimicking TSHoma. This case illustrates the diagnostic tests to distinguish an RTH-β from TSHoma.

KEYWORDS:

• Hyperthyroxinemia
• magnetic resonance imaging
• pituitary neoplasm
• thyroid function tests
• thyroid hormone resistance syndrome

Acknowledgments

We are grateful to Assistant professor Nuttha Sanghan, Department of Radiology, Prince of Songkla University, Hat Yai, Songkhla, Thailand, for the pituitary MRI information and Dr. Lalita Lohawijarn, Hat Yai hospital, Songkhla, Thailand, for taking care of the patient.

Disclosure statement

The authors report no conflicts of interest.

Ethical approval

This case report was approved by the Ethics Committee, Faculty of Medicine, Prince of Songkla University.