·
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.
·
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.
·
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.
·
·
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.
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