Pleiomorphism plurihormonal Pit-1-positive macroadenoma with central hyperthyroidism: a rare case report and literature review

BACKGROUND: Thyrotropin-secreting pituitary neuroendocrine tumors (PitNETs) are rare pituitary adenomas that are occasionally accompanied by hypersecretion of other anterior pituitary hormones, such as growth hormone (GH) and prolactin (PRL). The clinical, biochemical, and pathological characteristics may represent diverse circumstances. CASE PRESENTATION: In this report, a 33-year-old female diagnosed with a TSH PitNET co-secreting GH presented no obvious clinical symptoms. The main characteristics were elevated thyroid-stimulating hormone (TSH), free tri-iodothyronine (FT3), and free thyroxine (FT4) levels accompanied by slightly elevated GH and insulin-like growth factor-1 (IGF-1) levels. Magnetic resonance imaging (MRI) detected a pituitary macroadenoma (18 × 16 × 16 mm) with cavernous sinus and suprasellar invasion. Immunohistochemistry revealed diffuse positivity for TSH, strong immunoreactivity for GH, and sporadic positivity for PRL. The electron microscope and double immunofluorescence staining confirmed a plurimorphous plurihormonal adenoma producing TSH, GH, and PRL. After preoperative somatostatin receptor ligand (SRL) treatment and transsphenoidal surgery, the patient achieved temporary clinical and biochemical remission. However, 3 months after surgery, the patient was suspected of having Hashimoto’s thyroiditis due to higher thyroglobulin antibody (TGAb), thyroid peroxidase antibody (TPOAb), and thyroid receptor antibody (TRAb) and an enlarged thyroid nodule. During follow-up, thyroid function and TSH slowly transformed from transient hyperthyroidism to hypothyroidism. They were maintained in the normal range by L-T4. CONCLUSION: In the TSH PitNET, the positive immunohistochemistry for TSH, GH, and PRL translated into hormonal overproduction with TSH and GH. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12902-022-01220-2.