123I Imaging: A Useful Adjunct in the Evaluation of Infants with Mild Hyperthyrotropinemia

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SAT 622-631-Pediatric Endocrinology: Thyroid
Clinical
Saturday, June 15, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SAT-625
Evan Graber*1, Molly Oliver Regelmann2, Elizabeth Chacko3, Amy Buono4, Ahmed Khattab4, Michelle Klein5, Dennis Jay Chia6, Elizabeth Wallach4, Fenella Greig4, Chad Davis7, Rachel Annunziato6, Josef Machac5 and Robert Rapaport8
1Mount Sinai Hosp, New York, NY, 2Mount Sanai School of Medicine, New York, NY, 3Mount Siani Hospital, New York, NY, 4Mount Sinai School of Medicine, 5Mount Sinai Hospital, New York, NY, 6Mount Sinai School of Medicine, New York, NY, 7Fordham University, New York, NY, 8Mt Sinai Schl of Med, New York, NY
Background: Controversy exists regarding the clinical significance of mild, but persistent, elevations of TSH in infants.  In many, treatment is often initiated.  TRH testing is no longer available in the United States.  Ultrasound is able to demonstrate thyroid location and anatomy and technetium-99m imaging gives only limited information about thyroid function.  123I imaging demonstrates both structure and function of the thyroid gland.

Aim: Determine if 123I imaging may help support clinical decision-making regarding treatment in infants with mild hyperthyrotropinemia.

Methods: Retrospective chart review of clinically asymptomatic infants with mild elevations of TSH (5-20 uIU/mL) and normal free T4 and T3 values who underwent 123I imaging at Mount Sinai Medical Center between 2007 and 2013.  All studies were evaluated by a single observer (JM).  Images were obtained at 4 hours (h) and 24h after oral administration of 4uCi/kg of 123I.  Normal uptake values based on adult data were 6-12% at 4h and 10-30% at 24h.  Normal expected increase in uptake between 4h and 24h was ³50%.  Data collection included age at imaging, TSH value just prior to scan, 4h 123I uptake, 24h 123I uptake, and levothyroxine (LT4) dose 1 year after treatment initiation.

Results:  Twenty infants were identified.  None had evidence of recent iodine exposure.  Three had scans after 3 years of age for re-evaluation and were excluded from this analysis.  Of the remaining 17, 8 were male and all but 1 were appropriate in weight and length for gestational age.  TSH at the time of imaging was 4.72-17.12 uIU/mL (mean 8.74±3.4 uIU/mL).  Four had TSH >10 uIU/mL.  All had normally configured thyroid glands in eutopic locations and were placed on treatment after imaging.  There was no significant difference between the group of infants with TSH >10 compared with those <10 with respect to 123I uptake at 4h, 24h, or change in uptake at 24h compared to 4h.  Only 2/17 had 4h and 24h 123I uptake values close to standard normal adult values.  15/17 had abnormal imaging: 3 had high 123I uptake at 4 and/or 24h and 12 had low 4h uptake, low 24h uptake, and/or lack of an adequate increase in uptake between the 2 time points.  After 1 year of treatment the mean LT4 dose was 3.28±1.2 mcg/kg (mean age 1.34±0.45 yr).  There was no correlation between LT4dose and pre-treatment TSH or imaging result.

Conclusion:  Fifteen of the 17 infants (88%) had what appeared to be abnormal 123I imaging based on adult normative data suggestive of hypothyroidism and/or dyshormonogenesis, supporting initiation of treatment.  Genetic studies are needed to confirm their diagnoses.  We are unaware of any normative data for 123I uptake in infants.  Studies in additional patients are needed to confirm the value of 123I imaging in the evaluation and management of infants with mild hyperthyrotropinemia.

Nothing to Disclose: EG, MOR, EC, AB, AK, MK, DJC, EW, FG, CD, RA, JM, RR

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm