Syndrome of inappropriate secretion of thyroid-stimulating hormone in a subject with galactorrhea and menstrual disorder and undergoing infertility treatment: Case report

RATIONALE: Syndrome of inappropriate secretion of thyroid-stimulating hormone (SITSH) is a rare cause of hyperthyroidism. Thyroid-stimulating hormone (TSH) levels are usually normal or high, and triiodothyronine (FT(3)) and free thyroxine (FT(4)) levels are usually high in subjects with SITSH. PATIENT CONCERN: A 37-year-old woman had experienced galactorrhea and menstrual disorder for a couple of years before. She had undergone infertility treatment in 1 year before, hyperthyroidism was detected and she was referred to our institution. DIAGNOSIS: She was suspected of having SITSH and was hospitalized at our institution for further examination. The data on admission were as follows: FT(3), 4.62 pg/mL; FT(4), 1.86 ng/dL; TSH, 2.55 μIU/mL. Although both FT(3) and FT(4) levels were high, TSH levels were not suppressed, which is compatible with SITSH. In addition, in brain contrast-enhanced magnetic resonance imaging, nodular lesions were observed in the pituitary gland with a diameter of approximately 10 mm. In the thyrotropin-releasing hormone load test, TSH did not increase at all, which was also compatible with TSH-secreting pituitary adenoma. In the octreotide load test, the TSH levels were suppressed. Based on these findings, we diagnosed this subject as SITSH. INTERVENTIONS: Hardy surgery was performed after the final diagnosis. In TSH staining of the resected pituitary adenoma, many TSH-producing cells were observed. These findings further confirmed the diagnosis of pituitary adenoma producing TSH. OUTCOMES: Approximately 2 months after the operation, TSH, FT(3), and FT(4) levels were normalized. Approximately 3 months after the operation, she became pregnant without any difficulty. LESSONS: We should consider the possibility of SITSH in subjects with galactorrhea, menstrual disorders, or infertility. In addition, we should recognize that it is very important to repeatedly examine thyroid function in subjects with galactorrhea, menstrual disorder, or infertility.