Neuromuscular involvement in primary hyperparathyroidism.

Sixteen consecutive patients with primary hyperparathyroidism (HPT) were examined by a combination of electrophysiological, morphological and biochemical measurements. Six patients had, preoperatively, subjective impairment of neuromuscular function. Three of them were improved by the normalization of parathyroid function after surgery. In the other patients, who either had vague symptoms or appeared to be asymptomatic, the operation did not cause subjective changes in their neuromuscular function during a 3-month follow-up period. Altogether seven patients, three of whom had symptoms, had impairment of the neuromuscular transmission as evaluated by the single-fibre EMG technique. The changes were of slight degree and unlikely to be of clinical importance. Two patients had a slightly reduced nerve conduction velocity and in two cases moderate abnormalities were found in muscle biopsy specimens. In conclusion, the muscular weakness reported by HPT patients did not seem to be caused by disturbance of neuromuscular transmission. HPT patients who preoperatively were apparently asymptomatic did not have defects of their neuromuscular transmission that were of clinical significance.