The Quarterly Journal of Nuclear Medicine and Molecular Imaging 2021 Feb 10

DOI: 10.23736/S1824-4785.21.03344-6

Copyright © 2021 EDIZIONI MINERVA MEDICA

language: English

The role of the laboratory medicine in the diagnosis of the hyperthyroidism

Federica D’AURIZIO ✉

Clinical Pathology Institute, Department of Laboratory Medicine, Santa Maria della Misericordia University Hospital, Udine, Italy

Hyperthyroidism is a clinical condition characterized by inappropriately high synthesis and secretion of thyroid hormones by the thyroid gland. It has multiple aetiologies, manifestations and potential therapies. Graves’ disease is the most common form of hyperthyroidism, due to the production of autoantibodies against thyrotropin receptor, capable of over-stimulating thyroid function. A reliable diagnosis of hyperthyroidism can be established on clinical grounds, followed by the evaluation of serum thyroid functional tests (thyrotropin first and then free thyroxine, adding the measurement of free triiodothyronine in selected specific situations). The recent guidelines of both the American and European Thyroid Associations have strongly recommended the measurement of thyrotropin receptor autoantibodies for the accurate diagnosis and management of Graves’ disease. If autoantibody test is negative, a radioiodine uptake and thyroid scan should be performed. Taking into account the most recent laboratory improvements, thyroid binding inhibition immunoglobulin can be considered the best first solution for the measurement of thyrotropin receptor autoantibodies in diagnosis and management of overt cases of Graves’ disease. In fact, they have a satisfactory sensitivity and specificity (97.4% and 99.2%, respectively) being performed in clinical laboratories on automated platforms together with the other thyroid function tests. In this setting, the bioassays should be reserved for fine and complex diagnoses and for particular clinical conditions where it is essential to document the transition from stimulating to blocking activity or vice versa (e.g. pregnancy and post-partum, related thyroid eye disease, Hashimoto’s thyroiditis with extrathyroidal manifestations, unusual cases after LT4 therapy for hypothyroidism or after anti-thyroid drug treatment for Graves’ disease). Undoubtedly, technological advances will help improve laboratory diagnostics of hyperthyroidism. Nevertheless, despite future progress, the dialogue between clinicians and laboratory will continue to be fundamental for an adequate knowledge and interpretation of the laboratory tests and, therefore, for an accurate diagnosis and correct management of the patient.

KEY WORDS: Hyperthyroidism; Graves’ disease; Thyrotropin; Thyrotropin receptor; Free Thyroxine; Thyrotropin receptor antibodies; Bioassay; Immunoassay