Evaluation of thyroid hormones and thyroid-stimulating hormone levels in critically ill full-term newborns

Aim of the study
This study aimed to define the thyroid hormone characteristics in full-term critically ill neonates versus healthy neonates to evaluate the incidence of the euthyroid sick syndrome (ESS).

Material and methods
The present case-control study recruited 30 neonates presenting with manifestations of severe critical illness and a similar number of healthy controls. Patients were subjected to TT3, TT4, TSH, and FT4 testing.

Results
For the whole group of cases at the first sample the TT3-1 level was significantly lower than that of controls (85.63 ±33.380 ng/dl, 115.03 ±30.310 ng/dl, respectively) with a highly significant difference. The TT4-1 in cases on admission showed a highly significant difference to that of controls (7.607 ±2.2789 µg/dl, 11.219 ±2.088 µg/dl, respectively) (p < 0.01). TSH-1 in cases on admission was higher (6.573 ±6.6766 µIU/ml) than that of controls (3.964 ±4.5748 µIU/ml), but this did not show a significant difference (p > 0.05). In the second sample (5-6 days after the beginning of illness), TT3-2 (104.23 ±42.592 ng/dl) was still significantly less than that of controls (115.03 ±30.310 ng/dl), with a p-value < 0.05. TT4-2 (8.20 ±2.646), and still significantly lower than that of controls (11.219 ±2.088 µg/dl) with p-value < 0.05. TSH-2 in cases was higher (5.57 ±5.836 µIU/ml) than that of controls (3.964 ±4.5748 µIU/ml) with no significant difference (p > 0.05).

Conclusions
Critical illnesses are hallmarked by changes in circulating thyroid hormone parameters in full-term neonates with low TT3 concentrations in the absence of elevated TSH. The critically ill cases had a worse thyroid hormonal profile from the beginning of the disease until death compared with those who survived.