[Thyroid activity in patients with myasthenia]

In 27 patients with myasthenia thyroid function tests were done using radioassay methods. The levels of thyroxine (T4), triiodothyronine (T3), thyroxine-binding protein (BT4) and thyrotrophic hormone (TSH) were determined simultaneously in the serum. In 4 myasthenics the levels of T3 and T4 were determined after administration of exogenous TSH (Ambinon). The control group comprised 13 subjects without thyroid function disturbances. The investigations demonstrated a statistically significant decrease of T4 (at p less than 0.05) and T3 (at p less than 0.01) in myasthenia as compared with the control group. Administration of TSH raised the T3 level by 40% and that of T4 by 6%. The results obtained by the authors indicate presence of secondary hypothyroidism in myasthenia possibly due, to failure of the hypophyseo-hypothalamic system.