Inverse correlation of parathyroid hormone levels and endothelial function in patients with type 2 diabetes

Introduction:

Increased parathyroid hormone concentrations have been related to cardiovascular mortality. We hypothesized that intact parathyroid hormone (iPTH) levels also negatively correlate with flow-mediated dilatation (FMD).

Methods:

We examined brachial artery FMD, nitroglycerin-mediated dilatation (NMD) and pulse wave velocity (PWV) in participants of the German Diabetes Study (type 1 diabetes, T1DM: n = 19, age 32.6 ± 11.6 years, BMI 26.3 ± 5.3 kg/m², disease duration 1.0 ± 1.6 years; type 2 diabetes, T2DM: n = 32, 53.2 ± 12.3 years, 32.2 ± 5.3 kg/m², 2.1 ± 2.4 years; healthy controls, CON: n = 6, 43.7 ± 14.7 years, 28.2 ± 4.4 kg/m²) using B-mode ultrasonography. iPTH was measured with a chemiluminescence immunometric assay.

Results:

iPTH concentrations were comparable between groups (T1DM: 35.5 ± 16.8, T2DM: 41.3 ± 25.5, CON: 38.4 ± 8.3 pg/ml). Hypertension was present in 0%, 37.5% and 16.7% and dyslipidemia was present in 10.5%, 56.3% and 16.7% (T1DM, T2DM, CON). Only in T2DM, upon adjustment for age, sex and BMI, iPTH correlated negatively with FMD (r =-0.43, p < 0.05). The NMD response was lower in T2DM compared to CON (12.2 ± 4.6% vs. 18.5 ± 4.4%, p < 0.005) and similar to T1DM (13.1 ± 9.1%, n.s.). PWV (15 s after hyperemia) was lower in both T1DM and T2DM (141.4 ± 55.5 cm/s and 128.2 ± 55.0 cm/s vs. CON: 198.9 ± 25.4 cm/s, both p < 0.05). Both NMD response and PWV did not correlate with iPTH.

Conclusion:

Despite short disease duration, endothelial dysfunction is already present in patients with diabetes. Furthermore, iPTH could be an early biomarker for endothelial insulin resistance of T2DM.