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All rights reserved. doi:10.1016/j.ijcard.2010.10.122 Serum intact parathyroid hormone levels independently predict exercise capacity in stable heart failure patients Varvara Agapitou a , Stavros Dimopoulos a, ⁎, Anthi Mpouchla a , Lampros Samartzis a , Eleni Tseliou b , Elissavet Kaldara b , John Terrovitis b , Athanasios Tasoulis b , Eleni Karga c , Serafim Nanas a a 1st Critical Care Medicine Department, Cardiopulmonary Exercise Testing and Rehabilitation Laboratory, “Evgenidio” Hospital, NKUA, Athens, Greece b 3rd Cardiology Department, “Laiko” Hospital, NKUA, Athens, Greece c 2nd Endocrinology Department, “Alexandra” Hospital, NKUA, Athens, Greece article info Article history: Received 20 October 2010 Accepted 23 October 2010 Available online 15 December 2010 Keywords: Hyperparathyroidism Oxygen kinetics Exercise capacity Chronic heart failure ⁎ Corresponding author. 1st Critical Care Medicine Department, Cardiopulmonary Exercise Testing and Rehabilitation Laboratory, “Evgenidio Hospital”, National Kapodistrian University of Athens, 20, Papadiamantopoulou Str, Athens, 11528, Greece. Tel.: +30 210 7236743, +30 6973956974; fax: +30 210 7242785. E-mail address: a-icu@med.uoa.gr (S. Dimopoulos). Patients with chronic heart failure (CHF) are characterized by an elevation of intact serum parathyroid hormone (PTH) levels that seems to follow disease severity [1–3]. Several factors may contribute to the appearance of secondary hyperparathyroidism (SHPT) in CHF patients, including hypovitaminosis D, aldosteronism, chronic use of furosemide and impaired renal function [4–8]. CHF patients exhibit significant exercise intolerance manifesting by dyspnea and fatigue during their daily activities. Peak oxygen uptake (VO 2peak ) is the best predictor of exercise capacity and a powerful prognostic indicator in CHF patients [9]. The purpose of the present study was to investigate the association between PTH levels and exercise intolerance in CHF patients. We studied 35 consecutive outpatients of Caucasian race, living in the Mediterranean region with stable, mild to moderate CHF. All of them were under optimal medical treatment; with a Left Ventricular Ejection Fraction (LVEF) ≤45%. Exclusion criteria were any contraindication for the cardiopulmonary exercise testing (CPET), any disease affecting bone metabolism, and treatment with vitamin D (VitD) or calcium supple- ments or other hormone analogues. The baseline demographic and clinical characteristics of all patients are listed in Table 1. Informed consent was obtained from all patients, and the study was approved by the Human Study Committee of our Institution. All measurements were performed within spring months, in order to avoid the seasonal variation of VitD and PTH. The patients underwent a symptom-limited, ramp-incremental CPET on an electro-magnetically braked cycle ergometer and in the same week blood and urine samples were collected for the hormonal and biochemical analyses. Serum calcium concentrations were corrected for serum albumin, creatinine clearance was calculated by the Cockcroft–Gault formula and estimated glomerular filtration rate by the corrected Modification of Diet in Renal Disease study group formula (GFR MDRD ) [10]. No change in clinical status and medical treatment was observed during evaluation. Independent Samples t-test (or Mann Whitney tests in case of not normally distributed variables), were used for between groups com- parison of continuous variables. Pearson's or Spearman's (in case of not normally distributed variables) coefficient was used to assess correlations between variables. Values were considered to be signi- ficant at the 0.05 level of confidence. A multivariate linear regression analysis was performed to examine which variables were indepen- dently correlated with VO 2peak , including only those variables that demonstrated statistically significant correlation with VO 2peak in the univariate linear regression analysis . Patients were separated into two groups according to the PTH median value (=89 pg/ml) for descriptive purposes. Laboratory measurements are presented in Table 2. All parameters affecting body calcium homeostasis did not show any statistically significant difference between the two groups, except for the urinary N-telopeptide of type-I collagen (NTX) levels, a marker of bone resorption that were higher in 462 Letters to the Editor