Adipogenesis and TSH Receptor Expression
The symptoms and signs of Graves’ ophthalmopathy (GO) can be explained mechanically by an increase in the volume of tissues within the confines of the bony orbit. Volume measurements of the orbital adipose/connective tissue compartment and the extraocular muscles using computed tomography (CT) scans revealed abnormalities in 87% of Graves’ patients with clinically detectable GO (1). Enlarged muscles with normal fat volume was noted in 48% of these patients, while enlargement of both the extraocular muscles and the fat compartment was found in 46% of patients. The converse, or increased fat compartment volume with normal muscle volumes, was found in 8% of GO patients. In another study, measurement of extraocular muscle volumes in 50 patients with GO revealed relatively poor correlation between the extent of muscle enlargement and proptosis measurements. In contrast, another group of investigators found the degree of proptosis to correlate well with orbital fat volumes (2). Taken together, these studies suggest that orbital adipose tissue expansion in GO likely influences the degree of proptosis to a greater extent than does the extraocular muscle enlargement.
KeywordsAdipocyte Differentiation Extraocular Muscle Stromal Vascular Fraction Thyrotropin Receptor Orbital Fibroblast
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