Abstract
Postural orthostatic tachycardia syndrome (POTS) is a cardiovascular autonomic disorder with poorly understood etiology and underlying pathophysiology. Since cardiovascular morbidity has been linked to growth hormone (GH), we studied GH levels in patients with POTS. We conducted an age-sex-matched case–control study in patients with POTS (age 31 ± 9 years; n = 42) and healthy controls (32 ± 9 years; n = 46). Plasma GH levels were measured using high-sensitivity chemiluminescence sandwich immunoassay. The burden of orthostatic intolerance symptoms was assessed by the Orthostatic Hypotension Questionnaire (OHQ), consisting of a symptom assessment scale (OHSA) and a daily activity scale (OHDAS). POTS patients had significantly higher composite OHQ score than controls, more symptoms and less activity. Supine heart rate and diastolic blood pressure (BP), but not systolic BP, were significantly higher in POTS. Median plasma GH levels were significantly lower in POTS (0.53 ng/mL) than controls (2.33 ng/mL, p = 0.04). GH levels were inversely related to OHDAS in POTS and supine systolic BP in POTS and controls, but not heart rate neither group. POTS is associated with lower GH levels. Impairment of daily life activities is inversely related with GH in POTS. A higher supine diastolic BP is inversely associated with GH levels in POTS and healthy individuals.
Highlights
Postural orthostatic tachycardia syndrome (POTS) is a cardiovascular autonomic disorder with poorly understood etiology and underlying pathophysiology
Previous evidence based on high-throughput proteomics analysis by proximity extension assay (PEA) technique suggested that levels of circulating growth hormone (GH) might differ between patients with POTS and other possible autonomic disturbances with a history of syncope but normal response to tilt testing[8]
Supine heart rate and supine diastolic blood pressure (BP) were significantly higher in POTS patients compared with controls (69.0 ± 11.1 bpm vs. 63.3 ± 10.8 bpm, p = 0.02; and 72.9 ± 9.1 mmHg vs. 69.0 ± 8.5 mmHg, p = 0.04)
Summary
Postural orthostatic tachycardia syndrome (POTS) is a cardiovascular autonomic disorder with poorly understood etiology and underlying pathophysiology. Since cardiovascular morbidity has been linked to growth hormone (GH), we studied GH levels in patients with POTS. Supine heart rate and diastolic blood pressure (BP), but not systolic BP, were significantly higher in POTS. POTS can be physiologically classified based on patterns of peripheral blood flow and peripheral arterial resistance into low-flow POTS, normal-flow POTS and high-flow P OTS3 This variety of phenotypes suggests that POTS is a heterogenous syndrome with many manifestations sharing common pathophysiological mechanisms. Previous evidence based on high-throughput proteomics analysis by proximity extension assay (PEA) technique suggested that levels of circulating GH might differ between patients with POTS and other possible autonomic disturbances with a history of syncope but normal response to tilt testing[8]. Targeted proteomics is an ideal approach for establishing biomarker signatures in various clinical settings, dedicated detection methods and adequately matched control populations are key for external validation of PEA-guided biomarker discovery
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