Clinical and demographic factors associated with a delayed TSH rise in infants with congenital hypothyroidism: a retrospective review of a 10-year cohort in Indiana.

Introduction: The objective of our study was to determine the prevalence of a delayed thyroid-stimulating hormone (TSH) rise in infants with congenital hypothyroidism (CH) born in Indiana. Additionally, we sought to determine whether there are differences in clinical or demographic factors associated with this delayed cohort compared to those seen in infants detected early.

Methods: Newborn screen (NBS) results were collected for all cases of CH diagnosed between 2012-2022. Infants with a delayed TSH rise had an initial normal NBS followed by an abnormal NBS, and a confirmatory serum TSH value >20 mU/mL. Binary logistic regression was performed to identify if demographic and clinical factors (gestational age, birth weight, race, sex, ethnicity, and maternal age) were associated with a delayed rise in TSH. Linear regression was used to assess the relationship between TSH concentration versus selected factors and timing of diagnosis.

Results: 73 infants met our inclusion criteria for a delayed diagnosis (16% prevalence). Lower gestational age and birth weight Z scores were associated with higher odds of a delayed TSH rise (each p ≤ 0.001). Lower TSH values were also found to be associated with a delayed diagnosis (p=0.010).

Conclusion: Our study confirms that prematurity is a significant contributing factor for having a delayed diagnosis of CH. In contrast, other demographic factors such as race, sex, ethnicity, and maternal age do not appear to be associated with a delayed diagnosis. Other post-natal factors that may be associated with an increased risk of a delayed rise in TSH in infants with CH require further exploration.