Elevated inferior petrosal sinus levels of PTHrP in a patient with Cushing's disease

PTHrP has been found in various tissues, including prolactinomas and growth hormone producing adenomas, The function and clinical importance of PTHrP are poorly understood. We report the case of a 25-year-old female patient with hirsutism. Autonomous ACTH-dependent hypercortisolism was documented by endocrine testing. Magnetic resonance imaging (MRI) revealed a 3-mm intrasellar hypointense lesion in the left side of the pituitary gland. The inferior petrosal sinus sampling disclosed a gradient of ACTH left central/peripheral of 30.5 and right central/peripheral of 2.0 and suggested the diagnosis of a left-sided pituitary ACTH secreting microadenoma. Interestingly, we found elevated PTHrP levels in the left inferior petrosal sinus with a gradient of 4.7 compared to peripheral venous blood and of 3.6 compared to the right sinus. Our results fit very well to the concept of a para-/autocrine secretion of PTHrP which has been proposed recently and suggest a role in the regulation of cell growth of pituitary adenomas.