Treatment with angiotensin II receptor blockers (ARBs) had no effect on parathyroid hormone (PTH) concentrations in postmenopausal women with insufficient vitamin D levels and elevated PTH levels, according to new research published in Clinical Endocrinology.
Although emerging research supports a positive bidirectional and clinically relevant interaction between PTH and the renin-angiotensin-aldosterone system (RAAS), data are limited.
RAAS has been hypothesized to lower PTH levels, as higher levels could affect cardiovascular health adversely. In the current study, researchers investigated whether treatment with an ARB lowered PTH levels in postmenopausal women with high PTH levels caused by vitamin D insufficiency and whether the potential benefits of ARB therapy are influenced by normalizing vitamin D levels.
The initial cohort included 1580 women, with blood tests revealing that 109 women had high PTH and low 25(OH)D levels; 81 participants were included in the study. The participants were randomly assigned to receive either valsartan 80 mg/d alone, vitamin D3 70 μg/d only, both valsartan 70 μg/d and vitamin D3 70 μg/d, or double placebo.
Vitamin D3 supplementation reduced PTH levels by 3.4% vs an increase of 7.1 % in the placebo group (P =.01) and did not appear to have an effect on blood pressure, cardiac conduction, or concentrations of renin and aldosterone.
Valsartan did not have a significant effect on PTH compared with placebo and lowered average diastolic blood pressure by 5.9% compared with 1.9% for placebo (P <.05). Systolic blood pressure was nonsignificantly reduced by 6.4% for those receiving the ARB vs 4.3% for placebo (P =.18). The aldosterone/renin ratio was significantly reduced (P <.001) in the ARB group, but no significant interactions were observed whether ARB was given alone or in combination with vitamin D.
“We found no correlations between plasma concentrations of the calciotropic hormones and plasma concentrations of RAAS markers at baseline or after two weeks of intervention,” write the authors, adding that “this [speaks] against a direct interaction between the RAAS and calcium homeostasis in postmenopausal women with low vitamin D levels and high PTH levels as measured at screening.”
Bislev LS, Langagergaard Rødbro L, Nørgaard Bech J, et al. Effects of treatment with an angiotensin 2 receptor blocker and/or vitamin D3 on parathyroid hormone and aldosterone: a randomized, placebo-controlled trial [published online May 7, 2018]. Clin Endocrinol (Oxf). doi: 10.1111/cen.13734