Calcitonin values in pseudohypoparathyroidism

Pseudohypoparathyroidism type 1A is a rare endocrine disorder caused by GNAS mutation and the resulting hormone resistance at the receptor level, i.e. the activation of the intracellular pathway of the Gs alpha subunit is not possible. This disorder is most often characterized by resistance to the parathyroid hormone. However, it can also be characterized by resistance to other hormones, such as thyroid-stimulating hormone, gonadotropins (luteinizing and follicle-stimulating hormones), growth hormone-releasing hormone, and calcitonin. In this article, we describe the case of a patient diagnosed with pseudohypoparathyroidism based on phenotypic features of hereditary Albright osteodystrophy. Due to the progressive decline in intellectual functions and changing behavior, neurological examination confirmed calcifications of the CNS as part of Fahr's syndrome. During hospitalization, higher levels of thyroid-stimulating hormone and calcitonin were observed, probably as a result of resistance at the level of the receptor and its intracellular pathway. Hypercalcitoninemia occurs sporadically in cases involving pseudohypoparathyroidism type 1-a and type 1-b. Elevated levels of calcitonin should be evaluated by means of anamnesis and clinical examination involving morphological and functional tests, considering that a highly specific tumor is a marker of medullary carcinoma of the thyroid gland, as well as some neuroendocrine tumors. Some authors recommend fine needle aspiration biopsy in order to minimize the risk of medullary thyroid cancer.