Related Experiment Videos
Hypothyroxinemia in premature infants: is thyroxine treatment necessary?
1Quest Diagnostics, Nichols Institute, San Juan Capistrano, California 92690, USA. Fisherd@questdiagnostics.com
Insights
Monitoring thyroid function in very low birth weight (VLBW) infants is crucial. Early detection and treatment of transient hypothyroidism in VLBW infants may improve cognitive outcomes.
Area of Science:
- Neonatology
- Endocrinology
- Pediatric Health
Background:
- Increased survival of very low birth weight (VLBW) infants is linked to higher rates of transient thyroid dysfunction.
- VLBW infants exhibit low thyroxine-binding globulin (TBG) and thyroxine (T4) levels, alongside immature thyroid function and iodine deficiency.
- Nonthyroidal illnesses affect thyroid function in 30-60% of VLBW infants.
Purpose of the Study:
- To highlight the prevalence and diagnostic criteria for transient thyroid disorders in VLBW infants.
- To emphasize the importance of monitoring thyroid function in VLBW infants.
- To discuss the potential benefits of treating transient hypothalamic-pituitary hypothyroidism.
Main Methods:
- Observational analysis of thyroid function parameters in VLBW infants.
- Review of diagnostic criteria for primary and hypothalamic-pituitary hypothyroidism.
- Evaluation of preliminary data on treatment outcomes for transient hypothyroidism.
Main Results:
- VLBW infants have a high prevalence of transient primary hypothyroidism (0.41%) and hypothalamic-pituitary hypothyroidism (5-10%).
- Elevated serum TSH (> 20 mU/L) indicates primary hypothyroidism; low free T4 with normal/low TSH suggests hypothalamic-pituitary hypothyroidism.
- Preliminary data suggests treatment of transient hypothalamic-pituitary hypothyroidism may improve IQ at 2 years.
Conclusions:
- Thyroid function monitoring is essential in VLBW infants to detect transient and permanent hypothyroidism.
- Treatment for identified thyroid disorders is indicated.
- Further research is needed to confirm treatment benefits, diagnostic thresholds, and optimal dosing.
Abstract:
The increased survival of very low birth weight (VLBW) premature infants has been associated with an increased prevalence of transient disorders of thyroid function during the early weeks of life. All VLBW infants have relatively low, and gestation age-dependent, thyroxine-binding globulin (TBG) concentrations associated with variably low total thyroxine (T4) concentrations. These infants also have a high prevalence (30%-60%) of nonthyroidal illnesses that impact thyroid function, including total and free iodothyronine concentrations. Finally, thyroid gland hormone biosynthesis and the hypothalamic-pituitary axis are relatively immature and thyroid glandular iodine stores are low. As a result, VLBW infants manifest a high prevalence of transient primary hypothyroidism (0.41%) and transient hypothalamic-pituitary (thyrotropin [TSH] deficiency) hypothyroidism (5%-10%?). Thyroid function should be monitored in VLBW infants during the first 1-4 weeks of life to detect these disorders as well as the much less common permanent congenital hypothyroidism. An elevated serum TSH level (> 20 mU/L) is diagnostic of primary hypothyroidism and a low free T4 concentration with a normal or low serum TSH level suggests hypothalamic-pituitary hypothyroidism. Treatment of transient or permanent primary hypothyroidism and of congenital TSH deficiency is indicated. Preliminary data suggests that 30-60-day treatment of transient hypothalamic-pituitary hypothyroidism improves IQ at 2 years of age. However, further information confirming the benefit of treatment, the threshold free T4 values for diagnosis, and the optimal dose of T4 are necessary.