ABSTRACT
Electrodiagnostic changes typical of peripheral polyneuropathy have been reported in patients with over hypothyroidism. There are controversial reports regarding the effects of subclinical hypothyroidism on peripheral nervous system function. The aim of the present study is to investigate the possible effects of subclinical hypothyroidism of peripheral nervous system function by electrodiagnostic studies. A total of 28 patients [56 extremities] with subclinical hypothyroidism [defined as high serum TSH in the presence of normal free thyroxin by appropriate methods] including 25 adult females and 3 males [mean age of 46.07 +/- 6.87y] and 30 normal subjects as control group [60 extremities]. 27 females and 3 males [mean age 45 +/- 8.7y] had normal thyroid function tests enrolled in the study. Exclusion criteria were presence of diabetes mellitus, neuromuscular disorder, pregnancy, other disorders or drugs affecting neuromuscular function in all patients and control group. Electrodiagnostic studies including motor nerve conduction velocity [motor NCV], motor distal latency, CMAP Amplitude performed from tibial, median, peroneal and ulnar nerves bilaterally. Sensory function tests including sensory nerve conduction velocity, SNAP amplitude and sensory distal latency from median, ulnar and sural nerves bilaterally were studied by standard methods. Minimal f-response was studied from tibial, median and ulnar nerves bilaterally. Mean of sensory NCV, SNAP amplitude and sensory distal latency from median, ulnar and sural nerves and motor NCV, motor distal latency and CMAP amplitude from median, ulnar, personeal and tibial nerves and mean of minimal F-response of tibial, median and ulnar nerves were not significantly different in patients and control group. The results of this study shows that there is no functional impairment in peripheral nerves in subclinical hypothyroidism at the time of diagnosis