Diagnostic re-evaluation and predictors of congenital hypothyroidism with eutopic thyroid gland in Jiangxi, China

Iatrogenic hyperthyroidism in primary congenital hypothyroidism: prevalence and predictive factors

OBJECTIVES

Primary congenital hypothyroidism (CH) is a preventable cause of mental retardation. Iatrogenic hyperthyroidism has occasionally been reported using the recommended LT4 dosage. Currently, information regarding iatrogenic hyperthyroidism and predictive factors for permanent hypothyroidism (P-CH) among Thai patients is lacking. The aim of this study is to determine the prevalence and factors for predicting iatrogenic hyperthyroidism at one month after LT4 initiation and for predicting P-CH in primary CH infants.

METHODS

This retrospective cohort study involved 87 infants with primary CH. Patients were classified by thyroid status at one month after LT4 initiation. At 3 years, patients were reevaluated after LT4 cessation and assigned as P-CH or transient CH (T-CH). Differences between groups were analyzed.

RESULTS

One month after LT4 initiation, 35.6% of patients were classified as having iatrogenic hyperthyroidism. An initial LT4 dose of 10.2 μg/kg/day (sensitivity 64.5%, specificity 71.4%) was a suitable cutoff value for predicting iatrogenic hyperthyroidism, wherein 55.6 and 21.6% of patients were treated with initial doses of ≥10.2 and <10.2 μg/kg/day, respectively (p=0.004). Initial LT4 dose was the only predictive factor for thyroid status after initial treatment. At reevaluation, 47.4% of patients were diagnosed with P-CH. LT4 dosage at 3 years of age was significantly higher in patients with P-CH (3.3 vs. 2.85 μg/kg/day, p=0.02) and the only relevant factor for predicting P-CH.

CONCLUSIONS

Iatrogenic hyperthyroidism is common among infants with primary CH when treated with the recommended LT4 dosage. LT4 dose was the only factor for predicting iatrogenic hyperthyroidism after LT4 initiation and the diagnosis of P-CH.

Diagnostic Re-Evaluation and Potential Predictor Factors of Transient and Permanent Congenital Hypothyroidism in Eutopic Thyroid Gland

Background: The incidence of congenital hypothyroidism (CH) has increased over the years, and many predictors for detecting newborns with transient forms (TCH) as early as possible have been considered. Methods: All newborns diagnosed with primary CH and eutopic gland in the Piedmont region of Italy in the period of January 2014–June 2019 were enrolled and re-evaluated at the age of 2 years. Results: 105 newborns were diagnosed with CH during the study period. Dyshormonogenesis was observed in 55/105. At re-evaluation, we found that 52.7% had permanent CH (PCH), while 47.3% had TCH. Male/female rate, TSH levels at diagnosis, levothyroxine requirement at withdrawal and extra-thyroid congenital malformations rate were higher in the PCH group (p = 0.02, p = 0.009, p = 0.02 and p = 0.01), while fT4 levels at diagnosis were lower (p = 0.03). Sensitivity of 72.4% and specificity of 80.7% for serum TSH above 60 mcUI/mL, sensitivity of 73% and specificity of 72.4% for serum fT4 level below 7.2 pg/mL and sensitivity of 66% and specificity of 68% for drug requirement above 2.25 mcg/kg/day were observed in PCH. Conclusions: Demographic, clinical and hormonal data at diagnosis and levothyroxine requirement during the first two years should be adequately monitored to identify infants who are most likely to discontinue therapy after the age of 24 months.