The effect of l-thyroxine treatment on skin accumulation of acid glycosaminoglycans in primary myxoedema.

We assessed skin accumulation of acid glycosaminoglycans in ten patients with primary myxoedema (median age 70 years) before and during l-thyroxine treatment (median 7 months). Eight subjects matched for sex and age served as controls. Acid glycosaminoglycans were determined biochemically on small skin biopsies. Hyaluronic acid was elevated in untreated myxoedema, median 0.60, range 0.39-0.90 microgram hexosamine/mg dried defatted tissue compared to a median control value of 0.52, range 0.43-0.65 microgram hexosamine/mg dried defatted tissue, P less than 0.02. Chondroitin-4,6-sulphate and dermatan sulphate showed no elevation, while heparan sulphate was actually reduced in myxoedema, P less than 0.01. l-thyroxine treatment induced a significant reduction in hyaluronic acid, median 0.41, range 0.24-0.71 microgram hexosamine/mg dried defatted tissue, while no consistent changes occurred in the remaining three acid glycosamine glycans. The accumulation of hyaluronic acid might contribute to the peculiar non-pitting oedema of the skin in myxoedema, due to the strong water-binding capacity of the substance.