Thyroid disease in patients with McCune-Albright syndrome.

Involvement of the thyroid gland in the McCune-Albright Syndrome (MAS) is a common and sometimes overlooked feature of this disorder. The characteristics of the thyroid in MAS include isolated or combinations of generalized inhomogeneity, cystic and/or nodular features coupled with functional abnormalities. While most often the pathology is diffuse, it is rarely associated with compressive symptoms and signs. The functional abnormalities, which are seldom observed in the absence of underlying echographic structural changes, are characterized by autonomous function, frequently with a shifted T3/T4 ratio, suggesting an increase in intra-thyroidal conversion of the pro-hormone T4 into the active metabolite T3. While MAS-associated thyrotoxicosis is not always symptomatic, it is often linked with increased morbidity, especially in the presence of underlying conditions requiring surgical intervention. Although thyroid cancer has been described in two cases of MAS, the prevalence of malignancy does not appear to be high. The therapeutic options in MAS involvement of the thyroid gland include thionamides, 131Iodine and surgery.