Endocrine Abstracts

The co-existence of thyrotropin (TSH) and growth hormone (GH) secreting pituitary adenoma is exceedingly rare. Less than 15 cases having been reported.

Case report: A 75 years’ old man presented with new-onset atrial fibrillation. He had high FT4 with normal TSH. His ultrasound scan of the neck showed a solitary nodule. He had ablation twice and was started on bisoprolol and anticoagulant. He had an MRI scan for headaches and this showed a pituitary macroadenoma. He had high IGF-1. His oral glucose tolerance showed failure of GH suppression. His FT4 was persistently high with normal TSH and he had high subunits. This suggested the diagnosis of TSH and GH secreting pituitary adenoma.

Discussion: TSH-secreting pituitary adenomas are rare and not uncommonly, they co-secrete other pituitary hormones including growth hormones. Somatotrophs and lactotrophs share common transcription factors with thyrotrophs. TSH-secreting adenomas are benign but 60% of them are locally invasive. TSH-secreting pituitary adenomas typically present with either symptom of tumor growth like headache or visual field disturbance or symptoms of hyperthyroidism. Thyroid nodules are common in patients with TSHomas. In patients with TSH-secreting pituitary adenomas, the majority will need only surgery and radiation. The medical treatment used to normalize TSH and FT4 levels is somatostatin analogs. This is effective in about 90% of patients with TSH secreting pituitary adenomas TSHoma should be differentiated from resistance to the thyroid (RTH). The main difference between TSHoma and RTH is the presence of signs and symptoms of hyperthyroidism in patients with TSHoma, absence of family history, normal thyroid hormone levels in family members, and the presence of an elevated glycoprotein α-subunit in patients with a pituitary tumor.

Reference: LH Adams and D Adams. A case of a co-secreting TSH and growth hormone pituitary adenoma presenting with a thyroid nodule. EDM Case Reports 2018.