Endocrine Abstracts

Introduction: Hereditary hypophosphatemia (HH) are rare diseases, characterized by increased levels of fibroblast growth factor 23 (FGF23), excessive renal phosphate wasting and inappropriately low 1,25-dihydroxy-vitamin D causing hypophosphatemia. In children, the diseases manifest as rickets and osteomalacia, in adults only osteomalacia. Studies in cardiovascular risk among patients with HH are few and inconclusive. Some have found left ventricular hypertrophy in children and adolescents with X-linked hypophosphatemic rickets, but not in adults with HH. Isolated conditions with increased blood levels of FGF23 are not associated with increased risk of cardiovascular disease (CVD). However, complications to conventional medical treatment with phosphate and active vitamin D such as nephrocalcinosis and hyperparathyroidism are associated with increased cardiovascular risk. Pulse-wave velocity (PWV) is a measurement of arterial stiffness being an independent predictor cardiovascular risk.

Materials and methods: We performed a cross-sectional study of 50 adults with HH and 43 age- and gender-matched controls. Heart rate (HR), blood pressure (BP) and PWV were evaluated in the morning with the participants in a fasting state using the SphygmoCor® XCEL (AtCor Medical, Sydney, Australia). According to guidelines, PWV multiplied by 0.8 is reported.

Results: Mean systolic BP was significantly higher in HH (128, 95%CI: 124-133 mmHg) vs controls (118, 95% CI: 114-121 mmHg), P<0.001, as was diastolic BP: HH (75, 95%CI: 72-78 mmHg) vs controls (69, 95%CI: 67-72 mmHg), P=0.003. HR was significantly higher in HH (64, 95%CI: 61-66 s^-1) vs controls (59, 95%CI: 57-61 s^-1), P= 0.008. There was no statistically significant difference between groups for PWV: HH (6.7, 95%CI: 6.2-7.1 m/s) vs controls (6.2, 95%CI: 5.7-6.7 m/s), P=0.13.

Conclusion: In adults with HH, we found a significantly higher HR as well as a higher systolic and diastolic BP, which is associated with an increased risk for hypertension and CVD. Although PWV was not increased, our results suggest a higher risk for the development of hypertension and thereby CVD. We suggest measurements of BP and HR as routine workups by doctors taking care of adults with HH. Further studies are needed to explore eventual risks for hypertension and CVD in HH.