Assessment of Thyroid Profile in Critically Ill Patients and its Correlation with Prognosis

Abstract

Thyroid gland is the first endocrine gland to develop in humans. The hypothalamic-anterior pituitary axis play central role in the endocrine regulation of metabolic homeostasis. Decreased thyroid hormone levels lead to increased synthesis of hypothalamic thyrotropin-releasing hormone (TRH) which increases the secretion of thyroid-stimulating hormone (TSH) from the anterior pituitary. TSH stimulates the production of thyroid hormones from thyrocytes. Thyroid hormone homeostasis is also greatly affected in severely ill/critically ill patients.
Critical illness is the medical condition in which a patient, because of major surgery or severe illness, requires immediate intensive medical support of vital organ functions in order to survive. Independent of the underlying condition, critical illness is characterized by a uniform dysregulation of the hypothalamic– pituitary–peripheral axis and thereby there is alteration in the level of thyroid hormone, corticosteroid and sex hormones. This response occurs in biphasic pattern. This study is done to assess the thyroid profile in critically ill patients and its correlation with the prognosis. Also, to determine the association between the APACHE II scoring and thyroid profile among the study participants. To correlate the Thyroid function tests with the disease outcome of the critically ill patients.
Venous blood sample of 2 ml is collected and thyroid function is assessed using Chemiluminescent immunoassay method with other routine investigations like complete haemogram, renal function tests, liver function tests, arterial blood gas analysis, chest x ray, ECG. Thyroid function tests are compared with APACHE II score and analyzed whether they can predict the outcome of the patient.
Based on the current study findings, FT3 ≥ 2.01 and APACHE score ≤ 21.5 is the strongest predictor of mortality among critically ill patients. Though APACHE score value generally rises on uneventful outcome, the current study found that a value ≤ 21.5 had more accuracy with highest sensitivity, specificity in predicting the mortality outcome and also the predictive accuracy of Ft3 was even higher than APACHE scoring. Thus concluding that, in order to avoid uneventful outcome, appropriate monitoring, management and evaluation of FT3 levels is necessary among critically ill patients.