Value of parathyroid hormone level in differential diagnosis of patients with primary aldosteronism and nonfunctional adrenal tumors

  Background  Primary aldosteronism (PA) is one of the most common causes of secondary hypertension. Aldosterone-producing adenoma (APA) and idiopathic aldosteronism (IHA) are the most common types of PA. Studies have demonstrated that the parathyroid hormone (PTH) levels in PA and nonfunctional adrenal tumors (NFAT) are different.

  Objective  To investigate the differences of PTH level in PA and NFAT patients, as well as in APA and IHA patients, and discuss the value of parathyroid hormone level in the differential diagnosis of patients with primary aldosteronism and nonfunctional adrenal tumors.

  Methods  Clinical data about 414 PA patients (176 females, 238 males, average age of 50.90 ± 10.40 years, 263 cases of APA and 151 cases of IHA) and 275 NFAT patients (112 females, 163 males, average age of 52.74 ± 11.20 years) in the First Medical Center of Chinese PLA General Hospital from 2016 to 2020 were analyzed. The changes of biochemical indicators such as PTH, blood electrolytes, urine electrolytes, supine renin, supine aldosterone, ortho renin, ortho aldosterone and urine aldosterone were compared between PA, NFAT patients and APA, IHA patients. Then Pearson correlation analysis was adopted to investigate the factors affecting the PTH level.

  Results  Compared with the NFAT patients, PTH level in the PA patients elevated 64.82(62.36, 67.28) pg/mL vs 45.23(35.02, 54.74) pg/mL, P＜ 0.001. Compared with the IHA patients, PTH level in the APA patients elevated 65(51.28, 76.60) pg/mL vs 55.81(43.46, 68.15) pg/mL, P＜0.001. The PTH level was negatively correlated with blood potassium (r =-0.460, P＜0.001) and positively correlated with aldosterone (blood aldosterone r=0.293, P＜0.001; urinary aldosterone r=0.173, P＜0.001). ROC analysis results showed that the ROC-AUC (95% CI) of PTH to distinguish PA from NFAT was 0.742 (0.526 - 0.948), and the theoretical threshold was 52 pg/mL. The ROC-AUC (95% CI) for distinguishing the classification of APA from IHA in PA patients was 0.674 (0.375 - 0.967), and the theoretical threshold was 60 pg/mL.

  Conclusion  PTH level is different in PA and NFAT patients, as well as in APA and IHA patients. PTH levels are affected by serum potassium and aldosterone levels, and have certain reference value in the diagnosis and classification of PA.