Use of Tc-99 m thyroid scans in borderline congenital hypothyroidism.
BACKGROUND
Mild or borderline congenital hypothyroidism [often referred to as mild neonatal hyperthyrotropinemia (MNH)] is characterized by an abnormal newborn screen (NBS), followed by mildly elevated TSH and normal FT4 on confirmatory testing. This condition is increasingly observed, but data regarding optimal management are limited.


OBJECTIVE
Examine the use of routine technetium thyroid scanning (TS) in the management of MNH.


METHODS
Retrospective study of infants with MNH between 2000 and 2011. We assessed the clinical course of infants with MNH according to TS results; as a comparator, infants with classic congenital hypothyroidism (CH) were analysed in parallel.


RESULTS
We identified 69 infants (52% boys) with MNH and 164 (34% boys) with classic CH. TS results were divided into four subgroups: no uptake in 7% of MNH vs 24% of classic CH (P < 0·01), decreased uptake/anatomical abnormalities in 39% vs 46% (p = NS), increased uptake in 35% vs 26% (p = NS) and normal uptake in 19% vs 4% (P < 0·01). In MNH, neither NBS-TSH, confirmatory TSH and FT4, mean LT-4 treatment doses and number of dose escalations, nor post-treatment FT4 and TSH differed among the four subgroups. In contrast, clinical features in infants with classic CH differed among the subgroups. Among MNH infants who reached 3 years of age, trial-off treatment was successful in 6 of 11 (55%) with no apparent difference in success rates among TS subgroups.


CONCLUSIONS
The information provided by TS during evaluation of MNH does not predict clinical course; obtaining these scans in infants with MNH may not be an effective use of healthcare resources.
Division of Pediatric Endocrinology, The Hospital for Sick Children, Toronto, ON, Canada.|Department of Pediatrics, University of Toronto, Toronto, ON, Canada.
Asaf
A
Oren
Division of Pediatric Endocrinology, The Hospital for Sick Children, Toronto, ON, Canada.
Michael Ke
MK
Wang
Division of Pediatric Endocrinology, The Hospital for Sick Children, Toronto, ON, Canada.
Lori
L
Brnjac
Division of Pediatric Endocrinology, The Hospital for Sick Children, Toronto, ON, Canada.|Department of Pediatrics, University of Toronto, Toronto, ON, Canada.
Farid H
FH
Mahmud
Division of Pediatric Endocrinology, The Hospital for Sick Children, Toronto, ON, Canada.|Department of Pediatrics, University of Toronto, Toronto, ON, Canada.|Department of Physiology, University of Toronto, Toronto, ON, Canada.
Mark R
MR
Palmert
D003409:Congenital Hypothyroidism / Q000175:diagnosis* / Q000188:drug therapy; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D015997:Neonatal Screening / Q000379:methods*; D012189:Retrospective Studies; D013667:Technetium; D013972:Thyrotropin / Q000378:metabolism; D013974:Thyroxine / Q000627:therapeutic use
D013667:Technetium; D013972:Thyrotropin; D013974:Thyroxine