Abstract:

Objective Pronounced alterations in the hypothalamus-pituitary-thyroid axis occur during critical illness without any pathologic changes of the thyroid gland. It is referred to as non-thyroidal illness syndrome(NTIS) or euthyroid sick syndrome(ESS). And it is still controversy about whether reduction in circulating thyroid hormone is an adaptation resulting in a protection against catabolism or whether it is a maladaptation contributing to a worsening of the disease. So the aim of this study is: 1) to explore the profile of changes in thyroid function in the critically ill. 2) to explore the relationship between these endocrintic factors and metabolic states in critical illness with non-thyroidal illness syndrome.Methods Patients admitted to the ICU from September 2004 until December 2005 were eligible for enrollment in this study. Inclusion criteria were intensive care dependency with APACHE Ⅱ score over ten and with an expected stay in the ICU for at least another 48 h. Exclusion criteria were: ① age less than 18 yrs; ② preexisting neurological conditions; ③ hyperthyroidism hypothyroidism or other endocrine diseases; ④ intracranial lesions; ⑤ concomitant treatment with glucocorticoids and ⑥ pregnancy. A total of 38 patients with critical illness were investigated in this prospective clinical study, either with multiple organ dysfunction syndrome(MODS, n=13) or without MODS(n=25). Patients' age and APACHE Ⅱ scores were recorded at the first ICU-day and every 5th day. Serum T₃, T₄, thyrotropic-stimulating hormone(TSH), cortisol, growth hormone(GH) and insulin-like growth factor-1(IGF-1) were measured every 5-days; besides, the level of plasma albumin(ALB), prealbumin(PAB), transferrin(TRF) were measured at the same time. The data were analyzed by using T-test and bivariate correlations analysis. A P value <0.05 was regarded as statistically significant in all the tests conducted in this study. Data were expressed as Mean±S.Results Abnormality in circulating thyroid hormone was found in all patients in this study. The levels of serum thyroid hormone were declined markedly in patients with or without MODS(P<0.01). In MODS patients, recovery of declined of thyroid hormone wase slower than that in patients without MODS. A negati correlation was found between serum T₃ and cortisol and C reactive protein(P<0.05) in patients with acute critical illness, and a positive correlation was found between TSH and growth hormone(P<0.01) at the same time. No significant correlation was found between thyroid hormone and other hormones except cortisol in prolonged phase. Meanwhile, changes in blood levels of prealbumin and thyroid hormone were closely related(P<0.01).Conclusion Adjustments in the thyroid axis in critical illness include a rapid decrease in T3, the bioactive thyroid hormone. And there are no compelling data to administer thyroid hormone in the so-called non-thyroidal illness syndrome. Since non-thyroidal illness syndrome occurs in most patients with systemic illness, and because the morbidity and mortality rate of NTI is high, it becomes important to determine whether thyroid hormone administration is beneficial or detrimental. This clinical studyreveals that: 1) the hypothalamus-pituitary-thyroid axis is affected during critical illness. Thyroid hormone and TSH are decreased in critically ill patients and correlated with the severity of critical illness. 2) down-regulated function of the hypothalamus-pituitary axis is observed with decrease in TSH and growth hormone. 3) decrease in serum thyroid hormone is negatively associated with elevation in cortisol level negatively during prolonged critical illness. 4) changes in prealbumin relate positively to the level of thyroid hormone in prolonged ICU patients.

Key words: critical illness, thyroid hormone, cortisol, growth hormone, IGF-1, metabolism