Expanded Endoscopic Endonasal Transtuberculum Transplanum Resection of a Giant Thyroid-Stimulating Hormone Producing Macroadenoma: A Case Report

Thyroid-stimulating hormone (TSH) secreting tumors of the pituitary gland (TSHomas) are a rare tumor that represent up to only 1–2% of all pituitary lesions. TSHomas are often misdiagnosed by clinicians for disorders such as Grave's disease and it is not until patients complain of vision changes/loss that they present to a neurosurgeon. By this time, the tumor can be progressed to a giant macroadenoma (>4 cm) and is complicated by suprasellar extension and invasion. The first line treatment for TSHomas remains surgical resection of the tumor via the endoscopic endonasal approach (EEA), with the goal of removing the neoplastic tissue and returning normal pituitary function and subsequent thyroid hormone levels. We present the following case in support of endoscopic endonasal surgical resection as the first line treatment for TSHomas.

A 21-year-old male presented with a chief complaint of left vision loss and increased blurriness over the course of two months. MRI of the brain and orbits revealed a giant pituitary macroadenoma with suprasellar subarachnoid extension that mainly compressed the left optic nerve. Although no abnormal endocrinopathies were noted in the history and physical examination, laboratory values displayed an elevated TSH (7.936 uIU/mL) and free T4 (1.78ng/dL), thus the diagnosis of a TSHoma was made. Because of rapidly declining vision, we elected to pursue surgical resection of the tumor via endoscopic endonasal transtuberculum transplanum and transellar approaches. Intraoperative MRI demonstrated complete resection of the tumor with no signs of residual tumor. Immediately postoperatively, the patient's TSH levels began to normalize and vision improvement was noted. At 6 weeks follow-up, vision was completely restored and TSH and T4 levels were normalized (2.063 uIU/mL and 0.88 ng/dL, respectively). The patient experienced mild weight gain likely due to a decrease in TSH and subsequent T4 decrease. The patient is confirmed to be in remission with 6 months follow up.

The present case demonstrates an expanded endoscopic endonasal surgical success in achieving complete tumor removal, vision restoration, and re-normalization of TSH/T4 levels in a patient with a TSH-secreting macroadenoma. We recommend surgery as the first line management for TSHomas. Longer period of follow up is necessary to evaluate possible recurrence.