STAPEDIAL REFLEX - A BIOLOGICAL INDEX FOUND TO BE ABNORMAL IN CLINICAL AND SUBCLINICAL HYPOTHYROIDISM

There is only limited evidence for biological parameter abnormalities in subclinical hypothyroidism. The aim of this study was to investigat e the impact of varying degrees of thyroid failure on the stapedial re flex as a biological index, and establish its role in the evaluation o f the hypothyroid patient. We studied 10 patients with subclinical hyp othyroidism, 10 patients with clinical hypothyroidism, and 20 controls . All three parameters of stapedial reflex (amplitude, decay, and thre shold) were measured before and after restoration of euthyroidism thro ugh thyroxine administration. Data are given as mean a SEM. Stapedial reflex maximal amplitudes were different among the groups studied (p < 0.0001), as values in subclinical (4.3 +/- 0.4 mm) and clinical (3.7 +/- 0.3 mm) groups before treatment were lower (p < 0.05) than those o f control (5.7 +/- 0.3 mm), and subclinical (6.4 +/- 0.5 mm) and clini cal (5.6 +/- 0.4 mm) groups after treatment. Similarly, stapedial refl ex decays were different among the groups studied (p < 0.001), as valu es in subclinical (81 +/- 7 ms) and clinical (89 +/- 4 ms) groups befo re treatment were higher(p < 0.05) than those in control (65 +/- 2 ms) , subclinical (56 +/- 8 ms), and clinical (61 +/- 8 mm) groups after t reatment. There was no significant difference among the groups for sta pedial reflex threshold or significant correlation between stapedial r eflex parameters and thyroid function tests. Stapedial reflex, a biolo gical parameter that reflects neuromuscular status, is abnormal in pat ients with subclinical and clinical hypothyroidism and returns to norm al when clinical and biochemical euthyroidism has been achieved throug h thyroxine administration.