Serum levels of myoglobin in aged thyreopathic patients.

Serum concentrations of triiodothyronine (T-3), thyroxine (T-4) and myoglobin were determined by radioimmunoassay in 10 hypothyroid, 15 hyperthyroid and 14 euthyroid aged patients. The average ages were between 69 and 71 yr for these groups. The serum levels of T-3 and T-4 were typical for the clinical diagnosis and were accompanied by characteristic changes in the serum myoglobin concentrations. The hypothyroid, the euthyroid and the hyperthyroid groups displayed 107.0, 33.1 and 17.0 ng myoglobin per ml of serum, respectively. These differences are statistically highly significant. The authors are of the opinion that the serum myoglobin level depends on the myoglobin content of the muscle tissue, being higher in hypothyroid and lower in hyperthyroid patients as compared to the euthyroid persons.