Endocrine Pathology

·         The resin T3 uptake (RTU) essentially measures the TBG concentration by measuring the binding of radioactive T3 to TBG; note that this is not the serum T3 concentration. The same thing is essentially determined using the thyroxine uptake (TU). These values then can be used to artificially determine the free thyroxine index (FTI), which is an estimate of the free thyroxine.

·         Rarely, cases of Hashimoto’s thyroiditis may develop hyperthyroidism (Hashitoxicosis), while the combination of Hashimoto’s disease, pernicious anemia, and type I diabetes mellitus is called Schmidt’s syndrome. This is one type of multiglandular syndrome.

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·         There are two basic pathways that lead to the development of follicular carcinomas of the thyroid. One involves mutations of the RAS family of oncogenes, while the other involves a unique translocation between PAX8 and the peroxisome proliferator–activated receptor gamma (PPAR gamma), which forms a PAX8-PPAR-gamma fusion gene.

The PAX (paired box) genes are a family of related genes that code for transcription factors important for tissue development. Abnormalities of these PAX genes are associated with various diseases: PAX-2 with the “renalcoloboma” syndrome; PAX-3 with the Waardenburg syndrome (white forelocks of hair; eye colors don’t match); PAX-5 with lymphoplasmacytoid lymphoma; PAX-6 with aniridia and Wilm’s tumor; PAX-8 with follicular thyroid carcinoma; and PAX-9 with congenital absence of teeth.

·         Two major patterns of autoimmune poly-endocrine syndromes have been described. In addition to autoimmune adrenitis, patients with autoimmune polyendocrine syndrome type 1 (APS1) have chronic mucocutaneous candidiasis and abnormalities of the skin, nails, and teeth (ectodermal dystrophy). APS1 is also known as APECED (autoimmune polyendocrinopathy, candidiasis, and ectodermal dystrophy). In addition patients have other autoimmune disorders including autoimmune hypoparathyroidism, idiopathic hypogonadism, and pernicious anemia. APS1 results from mutations of the autoimmune regulator (AIRE) gene, the product of which is expressed primarily in the thymus. Autoimmune polyendocrine syndromes type 2 (APS2) is not associated with candidiasis, ectodermal dysplasia, or autoimmune hypoparathyroidism. Instead, autoimmune adrenalitis is present with autoimmune thyroiditis (Hashimoto’s thyroiditis) or type 1 diabetes mellitus.

·         Thymomas are tumors arising from thymic epithelial cells and are among the most common mediastinal neoplasms, especially in the anterosuperior mediastinum. Histologic sections reveal a proliferation of spindle-shaped cells. There is a scanty or rich lymphocytic infiltrate of T cells, which are not neoplastic, although their size and prominent nucleoli may cause histologic confusion with lymphoma. About 90% of thymomas are benign and occur at a mean age of 50 years.