Nonsurgical hypoparathyroidism is associated with skeletal muscle dysfunction and restrictive lung disease

Abstract Context Systematic assessment of skeletal muscle function is lacking in patients with nonsurgical hypoparathyroidism (HP). Whether muscle dysfunction involves respiratory muscles and results in restrictive lung disease (RLD) is not studied. Objective To assess skeletal muscle and pulmonary functions in patients with HP. Design Observational case–control study. Methods Thirty patients with HP (mean age 37.7 years, 60% males) and 40 age-, sex-, and body mass index (BMI)-matched healthy controls were assessed for skeletal muscle function by handgrip strength, the short physical performance battery (SPPB) test, dual-energy X-ray absorptiometry (DXA), and electromyography (EMG). Pulmonary function was assessed by spirometry, body plethysmography, diffusion lung capacity for carbon monoxide, and diaphragmatic ultrasound (DUS). Results Patients with HP had lower serum calcium (2.25 ± 0.15 vs 2.4 ± 0.12 mmol/L, P < .001), serum magnesium (median [interquartile range] 0.74 [0.69-0.82] vs 0.78 [0.69-0.90] mmol/L, P = .04), handgrip strength (18.08 ± 8.36 vs 22.90 ± 7.77 kg, P = .01), and composite SPPB scores (9.5 [7-10] vs 12 [12-12], P < .001) compared to healthy controls. Electromyographic evidence of myopathy was seen in 23% (5 of 22) of patients with HP but in none of the controls (P = .08). The prevalence of RLD was higher in the HP cohort compared to that in controls (24% vs 0%, P = .01). Diaphragmatic excursion (DE) (4.22 ± 1.38 vs 5.18 ± 1.53 cm, P = .01) and diaphragmatic thickness (DT) (3.79 ± 1.18 vs 4.28 ± 0.94 mm, P = .05) on deep inspiration were reduced in patients with HP. Conclusion Detailed testing of patients with HP without overt muscle and lung diseases revealed significant impairment in parameters of skeletal muscle function. Myopathy and RLD were observed in a considerable proportion of patients with HP.