Endocrine Abstracts

Introduction: Thyrotropin-secreting pituitary adenomas are rare tumors accounting for 1–2% of all pituitary adenomas and the diagnosis is based on the combination of high fT4 levels with normal to high TSH concentration in the presence of a pituitary adenoma. About one third co-secrete other hormones, of which, most frequently growth hormone (16%) followed by prolactin and gonadotropins.

Case report: A 60 years-old male patient presented in 2016 after the incidental finding of an 18×16×14 mm pituitary macroadenoma on a CT scan performed while investigating a lipothymic episode. His medical history revealed arterial hypertension and sinus node dysfunction that required permanent pacemaker. The initial laboratory investigations showed high fT4 (2.23 ng/dl, N: 0.89–1.76) and TSH in the upper normal limit (3.03 μUI/ml, N: 0.4–4) in addition to hypersomatotropism: high IGF1 (404 ng/ml, N: 81–225) unsupressed GH during OGTT (1.39 ng/ml). The clinical examination showed no features of acromegaly and no signs of hyperthyroidism. The thyroid ultrasonography described multinodular goiter and the visual field test were normal. Treatment with somatostatin analogs was initiated with a favorable biological (IGF1=222 ng/ml, TSH=1.12 μUI/ml, fT4=1.29 ng/dl) and imagistic response (mild tumor shrinkage: 16×14×14 mm). Considering a surgical intervention, treatment has been disrupted, leading to another increasing of IGF1, fT4 and fT3 levels, which confirmed the suspicion of a mixed TSH/GH cosecreting adenoma. Somatostatin analogs were reinitiated, but despite the initially favorable evolution and the thyroid axis mentained within normal limits, the last investigations showed unsupressed levels of GH (1.206 ng/ml) and high levels of IGF1 (304 ng/ml, N: 51–187), requiring the association of cabergoline (1 mg/4 days).

Discussion: This case highlights the unusual presentation of a TSH/GH co-secreting macroadenoma in an asymptomatic patient. According to literature, surgical cure rate in such cases is less than two thirds due to predominance of invasive, large, fibrous tumors with a high risk of recurrence. In addition, in this patient, considering the surgical risks, treatment with somatostatin analogs seemed to be the proper approach with an initial favorable biological and imagistic response. Despite the sustained response on the thyroid axis, the presence of hypersomatotropism requires the association of dopamine receptor agonists, also considering gamma knife radiotherapy.