Thyroid Hormone Profile in Ambulatory Heart Failure Patients attending Adult Outpatient Clinic at Kenyatta National Hospital, Nairobi, Kenya

Abstract

Background: Thyroid disorder affects 5–10% of the general population and can contribute to heart failure. Hypothyroidism leads to a decrease in the cardiac output by 30–50%. Heart failure affects approximately 23 to 37 million people worldwide. However, despite the known relationship between thyroid dysfunction and heart failure, there is still a paucity of evidence on the burden of thyroid dysfunction in heart failure and their association in the Kenyan population. Knowledge of the burden of thyroid dysfunction in heart failure is essential in guiding clinical decision making and improving outcomes in heart failure patients.

Objectives: To determine the prevalence of thyroid dysfunction and it’s correlation with the severity of heart failure in ambulatory heart failure patients attending adult outpatient clinic at Kenyatta National Hospital, Nairobi, Kenya.

Design: A descriptive cross-sectional study design of ambulatory patients with heart failure attending the outpatient cardiac clinic at the Kenyatta National Hospital.

Methods: Ambulatory heart failure patients with a diagnostic label of heart failure based on Framingham’s criteria were consecutively sampled. Patients with structural heart disease based on echocardiogram findings, on amiodarone, and those who declined consent were excluded from the study. The study included patients above 18 years. Chemiluminometric assay was used to measure free triiodothyronine, free thyroxine, and thyroid stimulating hormones levels using the Liaison test kits .Thyroid functionwas defined as either normal or abnormal based on thyroid function test at reference of: fT3 (2.2–4.2) pg/ml, fT4(0.8–1.7) ng/dl, TSH (0.3–3.6) Uiu/ml. The sample was characterised and overall prevalence, percentages, mean and standard deviation used. Association between severity of heart failure based on the New York Heart Association functional class, class 1 and 2 (early heart failure), class 3 (advanced heart failure) and thyroid dysfunction were assessed using Pearson’s chi-square test.

Results: Three hundred and four patients were sampled, two declined consent and 302 were recruited into the study. Most of the heart failures were caused by Hypertensive Heart Disease (HHD) (53.3%) and Dilated Cardiomyopathy (DCM) (30.8%). Seventy six point two percent had heart failure in class I and II. The overall prevalence of thyroid dysfunction was 36.8% (95% CI: 31.5; 42.4). Of those with thyroid dysfunction 66.7% (95% CI: 57.1; 75.3) were women and 33.3% (95% CI: 24.7;42.9%) were men. Older adults had a higher prevalence of thyroid dysfunction with 49.6% (95% CI:39.9; 59.2) and 23% (95% CI: 15.9; 32.4) among those aged 65-79 years and 50-64 years respectively; 78.4% of patients with thyroid dysfunction were 50 years and above. Prevalence of thyroid dysfunction was 28.8% (95% CI: 20.6; 38.2), 41.4% (95% CI: 32.2; 51.2) and 29.7% (95% CI: 21.4; 39.1) for patients in heart failure class III, II and 1 respectively. Subclinical hypothyroidism was 18.8%, (95% CI:14.6; 23.8), euthyroid sick syndrome was 9%, (95% CI: 6.0; 12.7) and primary hypothyroidism was 6%, (95% CI: 3.8; 9.7) were the most prevalent thyroid dysfunction subtypes. Secondary hyperthyroidism was 1.0%, (95% CI: 0.3; 3.1), subclinical hyperthyroidism was 1.0%, (95% CI:0.3; 3.1) , primary hyperthyroidism was 0.3%, (95% CI:0.1; 1.8) and free T3 toxicosis was 0.3%, (95% CI:0.1; 1.8) were the least subtypes of thyroid disorders. There was no significant association between thyroid dysfunction and severity of heart failure based on New York Heart Association functional class.

Conclusion: Prevalence of thyroid dysfunction in ambulatory heart failure patients is high. The most common subtype of thyroid dysfunction is hypothyroidism, with subclinical hypothyroidism being the most prevalent subtype. There is no significant association between thyroid dysfunction and severity of heart failure based on New York Heart Association (NYHA) functional class.