Severe obesity is associated with symptomatic presentation, higher parathyroid hormone levels, and increased gland weight in primary hyperparathyroidism

Abstract

Context: A relationship between primary hyperparathyroidism (PHPT) and obesity has been observed but is incompletely understood. Furthermore, obesity has been associated with vitamin D deficiency, suggesting that the three conditions may be linked.

Objective: We hypothesized that PHPT in morbidly obese patients is more severe and that the difference may be explained by vitamin D deficiency. DESIGN AND SETTING, PARTICIPANTS, AND OUTCOME MEASURES: Records of 196 patients with surgically treated PHPT and known body mass index (BMI) were examined. Patients were stratified into three BMI groups: group I (nonobese), BMI < 25 kg/m(2) (n = 54); group II (non-severely obese), BMI 25-34 kg/m(2) (n = 102); and group III (severely obese), BMI 35 kg/m(2) or greater (n = 40).

Results: Preoperative PTH levels were higher in group ΙΙΙ compared with group Ι (181 ± 153 vs. 140 ± 80 pg/ml, p = 0.04). Group III patients had larger tumors on average compared with group I (1.8 ± 1.5 vs. 1.04 ± 1.5 g, P = 0.0002). In group III, BMI positively correlated with parathyroid tumor weight (r = 0.5, P = 0.002). Postoperative PTH was higher in group III compared with group Ι (61 ± 41 vs. 44 ± 28 pg/ml, P = 0.02). There was higher frequency of depression, musculoskeletal symptoms, weakness, and gastroesophageal reflux disease in group III patients.

Conclusions: BMI positively correlated with parathyroid tumor weight independent of vitamin D. Severely obese patients have larger parathyroid tumor weight, higher pre- and postoperative PTH, and greater symptoms.

Figure 1

Primary hyperparathyroidism-specific symptom distribution. GERD, Gastroesophageal reflux disease. ‡, P = 0.03; *, P = 0.02; ¥, P = 0.02; γ, P = 0.04; §, P = 0.001.

Figure 2

Mean parathyroid tumor weight distribution across the three BMI groups. Star, Group I vs. group III (P = 0.0004); γ, group II vs. group III (P = 0.0006).

Figure 3

Relationship between BMI and tumor weight (A), preoperative 25-OH D (B), and preoperative serum PTH (C). A, r = 0.3, P < 0.001; B, r = 0.2, P = 0.02; C, r = 0.1, P = 0.2.

Figure 4

Representative hematoxylin and eosin-stained parathyroid tumor sections. Resected gland with fat content less than 5% and corresponding BMI of 42% (A), fat content 20% and corresponding BMI of 31 kg/m² (B), and fat content 90% and corresponding BMI of 36 kg/m² (C).