TSH-secreting pituitary adenomas and bone.

Abstract

TSH-secreting pituitary adenoma (TSHoma) is the rarest functioning pituitary tumor, with an increasing incidence over the last decades. Diagnosis is often delayed, exposing patients to a high risk of developing chronic complications of long-standing hyperthyroidism. Although thyroid hormone excess is a recognized cause of secondary osteoporosis, very few studies have investigated skeletal damage in patients with TSHoma, with data limited to bone turnover markers (BTM) and a study on the prevalence of radiological vertebral fractures (VFs) incidentally detected on chest X-ray, whereas data on bone mineral density (BMD) are anecdotal. Bone resorption is increased in TSHoma compared to controls, whereas few case reports described osteoporosis and spine fractures as early complications of TSHoma. A high prevalence of morphometric VFs was described in TSHoma compared to nonfunctioning pituitary adenoma (NFPA). Patients with fracture were older and had higher free thyroxine (fT4) levels than patients without fracture. In this specific setting, treatment with somatostatin receptor ligands seems to have a protective role on fracture risk. Based on this evidence, a comprehensive osteometabolic evaluation should be performed in all patients with TSHoma, including assessment of BTM, measurement of BMD, and morphometric evaluation of VFs, both at diagnosis and then during follow-up, particularly in patients at high risk for fragility fractures.