[Beta-2-microglobulin in hyperthyroidism]

The aims of the study were to clarify the cause of increased serum beta 2-microglobulin as a marker of thyroid hyperfunction. Serum beta 2-microglobulin was measured in 31 untreated hyperthyroid patients, all of them with normal renal function. Twenty-one subjects were affected by diffuse toxic goiter and 10 by toxic adenoma. Serum free thyroid hormones, TSH, anti-thyroglobulin and anti-microsomal antigen autoantibodies were determined, too. Thyroid hormone and creatinine levels did not differed between both sets of patients. beta 2-microglobulin was higher than normal in 90% of cases with diffuse toxic goiter and in 70% of those with toxic adenoma (p less than 0.05), but mean beta 2-microglobulin concentrations didn't differ between the two groups. No difference was found in beta 2-microglobulin levels in diffuse toxic goiter group according to the presence or absence of autoantibodies. beta 2-Microglobulin and thyroid hormones were not correlated in either diffuse toxic goiter and toxic adenoma groups. These data confirm the high prevalence of elevated beta 2-microglobulin concentrations in hyperthyroidism. As renal function was normal, this rise is due to beta 2-microglobulin overproduction. This increased production is a hormone mediated effect, even if lymphocyte activation may contribute in diffuse toxic goiter. beta 2-microglobulin is not correlated with thyroid hormone concentrations so that at present it isn't a useful marker of hyperthyroidism severity for practical purposes.