Detectability of Subclinical Hypothyroidism and Thyroid Stimulating Hormone Levels Associated with Cardiovascular Diseases in Patients of North-West Region Hospital

Increased thyroid stimulating hormone (TSH) levels are detected quite often especially in older patients. Increased TSH level doesn't usually indicate the formation of persistent hypothyroidism and may be due to concomitant somatic disorders. Determining the threshold values of TSH associated with cardiovascular diseases (CVD) is an important clinical task.

Aim. To study the detectability of subclinical hypothyroidism, the range of thyroid-stimulating hormone values associated with CVD in patients who seek medical care at the multidisciplinary hospital of the North-West region.

Material and methods. 1340 patients of different sex and age with normal TSH value (0.4-2.5 mlU/l) and subclinical hypothyroidism were included into the study. Subclinical hypothyroidism was considered an increase in TSH level >4.0 mlU/L, provided that the level of free T4 is normal. According to electronic case histories in all patients, CVD (hypertension, coronary heart disease, heart failure, arterial atherosclerosis of the lower extremities) and a history of cardiovascular events (unstable angina, acute myocardial infarction, stroke and transient ischemic attack) were analyzed. For data processing the program Statistica, version 1 2 was used.

Results. The detectability of subclinical hypothyroidism was 1 0.2%, manifest hypothyroidism - 2.4%. In patients with subclinical hypothyroidism, CVD were detected significantly more often than in patients with euthyroidism (p<0.05). Subclinical hypothyroidism increased the likelihood of CVD in the middle age group (odds ratio [OR] 1.62; 95% confidence interval [95%CI] 1.39-1.89), in elderly patients (OR 3.84; 95%CI 2.95-4.99), and in patients 75 years and older (OR 2.53; 95%CI 1.84-3.50). Using the discriminant analysis, a mathematical model was built which allows predicting the development of CVD according to the TSH level of (accuracy - 66.7%, sensitivity - 22.3%, specificity - 96.8%). The estimated threshold TSH was 6.68 mlU/L. Patients with TSH levels <6.68 mlU/L have a high probability that they are healthy (96.8%), and elevated TSH levels (<6.68 mlU/L) are probably not associated with CVD.

Conclusion. An association of subclinical hypothyroidism with coronary heart disease, hypertension and CVD in general has been established. A TSH level of less than 6.68 mlU/L is probably not associated with CVD and does not require active treatment.

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