Pituitary adenoma secondary to primary hypothyroidism: Two case reports.

[RATIONALE] Primary hypothyroidism is characterized by loss of thyroxine feedback inhibition and overproduction of thyrotropin-releasing hormone, which might result in reactive pituitary hyperplasia. However, pituitary adenoma secondary to primary hypothyroidism is extremely rare and usually underdiagnosed, and the pathogenic mechanism remains unclear. Herein, we reported two cases with pituitary adenoma secondary to primary hypothyroidism.

[PATIENT CONCERNS] Case 1: A 35-year-old man presented to the local clinic with a 2-year history of fatigue, puffiness in the bilateral lower extremities and facial region, and coarseness of facial features. Additionally, his relatives also supplemented that he suffered from hypomnesis and hypophrenia.Case 2: A 56-year-old, postmenopausal woman presented to the local clinic with fatigue, dry skin, and sluggishness.

[DIAGNOSES] The pathological diagnosis of two patients was plurihormonal pituitary adenoma.

[INTERVENTIONS] A microscopical tumorectomy was performed when the two patients were admitted to our hospital. Thyroid hormone replacement therapy (thyroxine 50 μg/day) was prescribed after microsurgery.

[OUTCOMES] After 32 months (Case 1) or 43 months (Case 2) follow-up respectively, there was no recurrence, and the symptoms were completely relieved.

[LESSONS] Pituitary hyperplasia caused by primary hypothyroidism responds well to thyroid hormone replacement therapy. It is worth noting that repeated detection of serum T3, T4, and thyroid-stimulating hormone (TSH) should be performed 3 months after replacement therapy. If the results showed that TSH level decreased partly, while thyroid function did not improve significantly, long-term increased secretion of pituitary TSH adenoma should be considered. And microsurgical resection via a transsphenoidal approach could be ordered. If the optic nerve or optic chiasm were pressed by the adenoma, microsurgery should be performed to relieve the pressure immediately. And then, thyroxine tablet substitute therapy should be performed after surgery.