Stapedial Reflex: A Biological Index Found to be Abnormal in Clinical and Subclinical Hypothyroidism

Abstract

There is only limited evidence for biological parameter abnormalities in subclinical hypothyroidism. The aim of this study was to investigate the impact of varying degrees of thyroid failure on the stapedial reflex as a biological index, and establish its role in the evaluation of the hypothyroid patient. We studied 10 patients with subclinical hypothyroidism, 10 patients with clinical hypothyroidism, and 20 controls. All three parameters of stapedial reflex (amplitude, decay, and threshold) were measured before and after restoration of euthyroidism through thyroxine administration. Data are given as mean +/- 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 of control (5.7 +/- 0.3 mm), and subclinical (6.4 +/- 0.5 mm) and clinical (5.6 +/- 0.4 mm) groups after treatment. Similarly, stapedial reflex decays were different among the groups studied (p < 0.001), as values in subclinical (81 +/- 7 ms) and clinical (89 +/- 4 ms) groups before treatment were higher (p < 0.05) than those in control (65 +/- 2 ms), subclinical (56 +/- 8 ms), and clinical (61 +/- 8 mm) groups after treatment. There was no significant difference among the groups for stapedial reflex threshold or significant correlation between stapedial reflex parameters and thyroid function tests. Stapedial reflex, a biological parameter that reflects neuromuscular status, is abnormal in patients with subclinical and clinical hypothyroidism and returns to normal when clinical and biochemical euthyroidism has been achieved through thyroxine administration.

Clinical Profile of Subclinical Hypothyroidism:A Retrospective Study

“…[15] Painful neuropathies and neuromuscular abnormitieswere reported to be relieved with hormone replacement therapies. [16,26] The most frequent presenting complaint in this study was body pains. Symptoms were also a major impetus to initiate treatment with low dose levothyroxine.…”

Subclinical Hypothyroidism Is Mild Thyroid Failure and Should be Treated

“…Depression (19 -23), memory loss (2,19,24), cognitive impairment (25) and a variety of neuromuscular complaints (26,27) have all been reported to occur more frequently in patients with this condition. Objective peripheral nerve dysfunction, manifested by decreased conduction amplitude in peripheral nerves (28), and an abnormal stapedial reflex (29) have been demonstrated in these patients. Skeletal muscle abnormalities, including elevated serum creatine phosphokinase levels (30), increased circulating lactate levels during exercise (26), and repetitive discharges on surface electromyography (27), have also been reported.…”

The Clinical Significance of Subclinical Thyroid Dysfunction

“…Impaired glycogenolysis (239,240), alterations in myosin heavy chain expression (241), and reduced mitochondrial activity have been implicated in this process (242,243). The amplitude of the stapedial reflex, a biological parameter that reflects neuromuscular status, was abnormal in patients with subclinical and overt hypothyroidism (244). On the other hand, distal motor latencies, motor and sensory amplitudes, and nerve conduction velocities were not abnormal in patients with mild thyroid hormone deficiency (245).…”