Nociceptive threshold in hypothyroid patients.

The purpose of this study was to measure the nociceptive threshold in hypothyroid patients by determining when the nociceptive flexion reflex of the lower limb occurs under percutaneous electrical stimulation of the sural nerve, given that this threshold is well correlated with pain sensation. Twelve hypothyroid patients and twelve control subjects participated in the study. In the case of the hypothyroid patients, the nociceptive flexion reflex (or RIII reflex) was measured before and six weeks after the onset of substitution treatment. The results clearly indicate that the nociceptive threshold of the patients with hypothyroidism was significantly higher than that of the control subjects. After six weeks of substitution treatment, the RII threshold return to normal. The analgesia observed in the hypothyroid patients in this study do not appear to be correlated with the blood TSH level. The possible mechanisms of these analgesic effects are discussed.