Peripheral Nerve Function in Subclinical Hypothyroidism: A Case-Control Study

Peripheral nerve dysfunction is a well docu-mented feature of clinical hypothyroidism. Only a few studies have evaluated the functional al-terations in central and peripheral nervous sys-tems in subjects with subclinical hypothyroid-ism and results obtained have been controver-sial. The purpose of the present study was to in-vestigate the effects of subclinical hypothyroid-ism on peripheral nerve function. Twenty-eight individu-als (25 females and 3 males) with subclinical hy-pothyroidism (defined biochemically as high se-rum TSH with simultaneously normal serum free T4) as the study group and 30 age and sex matched subjects (27 females and 3 males) with normal thyroid function tests as the control group were enrolled into the study. None of the patients or controls had history of diabetes mel-litus, neuromuscular, metabolic, vasculitic or rheumatologic diseases or were taking medica-tions that may alter central or peripheral nerve function. Standard electrodiagnostic methods were used to study motor parameters including motor nerve conduction velocity, distal motor la-tencies, compound muscle action potential am-plitude from median, ulnar, tibial and deep per-oneal nerves, minimal-F-response from tibial, median and ulner nerves and sensory parameters including sensory nerve conduction velocity, sensory nerve action potential amplitude and distal sensory latencies from median, ulnar and sural nerves. In all patients and controls, values were obtained from both right and left sides. Values from patients were compared with those of controls by unpaired student''s t-test. Motor and sensory nerve function val-ues obtained from this electrophysiological study yielded no significant differences between patients with subclinical hypothyroidism and those with normal thyroid function. The results of this study show that there are no significant alterations in peripheral nerve function in patients with subclinical hypo-thyroidism.