SUN-457 Calcium Dynamics in Primary Aldosteronism: Comparative Analysis of Subtypes and Treatment Modalities

Abstract Disclosure: T. Nakamura: None. I. Kurihara: None. Y. Mizutani: None. K. Kinouchi: None. S. Kobayashi: None. K. Hayashi: None. Primary aldosteronism (PA), the leading cause of secondary hypertension, is associated with significant cardiovascular and renal complications independent of blood pressure control. Recent studies have also identified disturbances in calcium (Ca) dynamics in PA patients, including increased urinary Ca excretion and secondary hyperparathyroidism, which contribute to reduced bone mineral density (BMD) and elevated fracture risk. While targeted treatments such as adrenalectomy and mineralocorticoid receptor antagonists (MRAs) mitigate these morbidities, the clinical characteristics of each PA subtype and the impact of each treatment modality on Ca dynamics remain poorly understood. Although adrenalectomy is superior to MRA in preventing cardiovascular and renal disorders, its superiority in correcting Ca dynamics is unclear. This study retrospectively investigated Ca dynamics across PA subtypes—unilateral PA (UPA) and bilateral PA (BPA)—and evaluated the therapeutic effects of adrenalectomy and MRA in the largest PA cohort for this context (n = 352). PA patients exhibited significantly higher urinary fractional excretion of Ca (FECa: 1.28% vs. 1.04%, P < 0.001) and elevated parathyroid hormone (PTH) levels (60.0 pg/mL vs. 57.0 pg/mL, P = 0.047) compared to non-PA patients, independent of blood pressure control. They also required higher doses of antihypertensive medications, had increased urinary albumin levels, and required more potassium supplementation, consistent with previous studies. These abnormalities were more pronounced in UPA (FECa: 1.49%, PTH: 74.8 pg/mL), reflecting its greater severity compared to BPA. Post-treatment analysis showed that adrenalectomy for UPA and MRA for BPA effectively reduced urinary Ca excretion, increased serum Ca levels, and lowered PTH levels. These changes were accompanied by a decrease in estimated glomerular filtration rate (eGFR), improvement in urinary albumin, and elevated serum potassium. As most UPA patients received MRA until adrenalectomy, a comparative analysis of Ca dynamics was conducted between each post-treatment period for UPA patients who were examined both post-MRA and post-adrenalectomy. Notably, adrenalectomy further reduced urinary Ca excretion and improved PTH levels beyond the effects of MRA (FECa: 0.71% post-MRA vs. 0.39% post-adrenalectomy; PTH: 55.8 pg/mL post-MRA vs. 45.0 pg/mL post-adrenalectomy). These findings highlight PA subtype-specific differences in Ca dynamics and the distinct therapeutic effects of adrenalectomy and MRA. The additional benefits of adrenalectomy over MRA in UPA suggest its superiority in addressing hypercalciuria and secondary hyperparathyroidism, as shown in the cardiovascular protective effect. Further research is warranted to evaluate the long-term impact of these treatments on BMD and fracture risk, optimizing PA management strategies. Presentation: Sunday, July 13, 2025