The Role of ¹²³I Imaging in the Evaluation of Infants with Mild Congenital Hypothyroidism

Abstract

Background/Aims: Controversy exists regarding the diagnosis and treatment of mild congenital hypothyroidism (MCH). We studied the value of ¹²³I imaging in patients with MCH. Methods: Retrospective chart review of infants and children <4 years of age who underwent ¹²³I imaging: group 1 = MCH [thyroid-stimulating hormone (TSH) <25 µIU/ml, normal free T₄/T₃], group 2 = severe congenital hypothyroidism (TSH ≥25 µIU/ml), and group 3 = MCH in infancy imaged after treatment withdrawal at age 3 years. Data collected included 4- and 24-hour ¹²³I uptake, TSH, free T₄/total T₃ at imaging, age at imaging, and levothyroxine (<smlcap>L</smlcap>-T₄) dose at 1 year of. Results: Thirty-six patients underwent ¹²³I imaging. In group 1 (n = 20, median TSH: 8.49 µIU/ml), 85% had abnormal imaging consistent with dyshormonogenesis. Two patients were referred after 1 year of age. The median age at imaging for the remaining 18 patients was 54 days. Median <smlcap>L</smlcap>-T₄ dose at 1 year of age for these 18 patients was 2.8 μg/kg, which is consistent with dyshormonogenesis. Ninety-one percent of group 2 (n = 11, median TSH: 428.03 µIU/ml) had abnormal imaging. The median age at imaging was 13 days. Four patients in group 3 had abnormal ¹²³I imaging and restarted treatment. Conclusion:¹²³I imaging is a valuable tool for evaluation, diagnosis, and treatment of MCH.

Congenital Hypothyroidism: A 2020–2021 Consensus Guidelines Update—An ENDO-European Reference Network Initiative Endorsed by the European Society for Pediatric Endocrinology and the European Society for Endocrinology

“…The latter isotope needs later image acquisitions (at 2-3, and 24 hours), but provides more contrast and adds information about organification process, allowing perchlorate discharge testing when the thyroid is eutopic (64,65). Furthermore, it exposes infants to a lower dose of whole-body irradiation than 99m Tc (3-10 lCi/kg vs. 50-250 lCi/kg body weight) (66,67).…”

Feasibility of an Early Discontinuation of Thyroid Hormone Treatment in Very-Low-Birth-Weight Infants at Risk for Transient or Permanent Congenital Hypothyroidism

“…The 24 infants in the present study who were ultimately diagnosed with THT were treated with an average thyroxine dosage of 1.96 ± 0.56 μg/kg/day and all of them except 1 infant received lower thyroxine supplementation than the suggested dosage (3.25 μg/kg/day) that has been reported to represent a risk for PHT in a previous study [11]. Thyroid imaging also provides useful information regarding the distinction between potentially transient and definitely permanent CH [50]. A normal-sized eutopic thyroid gland is indicative of transient CH, whereas abnormal thyroid imaging results predict permanent CH [41,51].…”