Effects of smoking on severity of disease in primary hyperparathyroidism

In healthy subjects, smoking is associated with lower plasma levels of parathyroid hormone (PTH) and decreased bone mineral density (BMD). The effect of smoking on PTH, skeletal metabolism, and size/histology of the parathyroid glands in primary hyperparathyroidism (PHPT) is unknown. We investigated, in a cross-sectional study, whether smoking affects PTH levels, BMD, and weight/histology of removed parathyroid tissue in PHPT. We studied 344 (285 women) parathyroidectomized patients with PHPT (24% smokers). Biochemistry was determined at the time of diagnosis. BMD was measured before and after surgical cure. Smoking was associated with lower PTH (9.9 ± 1.8 [SD] vs. 12.2 ± 1.8 pmol/l, P < 0.01) and higher phosphate (0.95 ± 0.17 vs. 0.86 ± 0.17 mmol/l, P < 0.01) levels. Adjustments for between-group differences in age, sex, body weight, plasma creatinine, and 25-hydroxyvitamin D (25OHD) levels did not change the findings. Neither weight of removed adenomatous and hyperplastic tissue nor BMD differed according to smoking status. After adjustment for body weight, age, sex, and 25OHD levels, smokers had slightly lower BMD at the whole body but not at the spine, hip, or forearm. Independent of smoking status, surgical cure caused a significant increase in BMD at all measurement sites. In PHPT smoking is associated with lower plasma PTH and higher phosphate levels. Adjustment for confounders of PTH did not change the results. In contrast to healthy subjects, smoking seems not to decrease BMD in PHPT. Smoking may compromise the correct diagnostic evaluation of borderline hyperparathyroidism. It is unknown to what extent smoking in PHPT affects fracture risk and indication for surgery.