Muscle Function Is Impaired in Patients With “Asymptomatic” Primary Hyperparathyroidism

Abstract

Patients with "asymptomatic" primary hyperparathyroidism (PHPT) often describe improvement after surgery. We evaluated muscle and balance function, quality of life (QoL), and well-being in 58 PHPT patients and 58 population-based matched controls in a cross-sectional study. We tested whether patients considered "asymptomatic" according to international guidelines have functional impairment. Mean age of the patients and controls was 59 years, and 47 (81%) were women. Patients had higher levels of plasma PTH and ionized calcium. Creatinine and 25-hydroxyvitamin D levels did not differ between groups. Altogether, 16 (28%) patients were "asymptomatic." Compared with controls, PHPT was associated with significantly lower QoL in all eight domains of the short form-36 questionnaire, lower well-being (WHO Five Well-Being Index; p<0.001), and impaired postural stability during normal standing with eyes open (p<0.05) or closed (p<0.001). Maximum isometric muscle strength was reduced in both upper (p<0.01) and lower (p<0.001) extremities. Physical performance was decreased during 10 repeated chair stands (p<0.001) and time to walk 3m forward and back (p<0.05). Restricting analyses to "asymptomatic" patients showed significantly lower muscle strength at knee extension and flexion and impaired postural stability than in matched controls. PHPT is associated with deleterious effects on muscles and QoL. Impairments also apply to patients with mild disease, normally considered "asymptomatic." This may explain why "asymptomatic" patients report improvements following surgery. The impaired muscle function may contribute to increased fracture risk independent of bone mineral density.