Elimination kinetics of maternally derived thyrotropin receptor-blocking antibodies in a newborn with significant thyrotropin elevation.
OBJECTIVE
To determine the course of maternally derived elevations in thyrotropin-binding inhibitory immunoglobulins in a neonate.


METHODS
Case report.


METHODS
University pediatric endocrinology clinic and endocrine immunology laboratory in Ohio.


METHODS
An infant with elevated thyrotropin levels but near-normal total thyroxine levels, and her mother.


METHODS
None.


RESULTS
Thyroid hormone, thyrotropin, and thyrotropin-blocking immunoglobulin concentrations were serially measured in a woman and her infant, who was found to have elevated thyrotropin levels (234 mU/L) and borderline low thyroxine levels (95 nmol/L). As infant thyroxine concentrations remained normal (125 to 145 nmol/L), no thyroxine supplementation was given. Thyrotropin levels decreased concomitantly with thyrotropin-blocking inhibitory immunoglobulin levels, and normalized by day 56 of life. The apparent elimination half-life of thyrotropin-blocking immunoglobulins was 7.5 days.


CONCLUSIONS
The observed parallel elimination kinetics suggest that the thyrotropin receptor antibody acts as a thyrotropin antagonist, resulting in compensatory thyrotropin elevations. The duration of such elevations may be predicted on the basis of such elimination.
Division of Pediatric Endocrinology and Metabolism, Rainbow Babies and Children's Hospital, Cleveland, Ohio.
A L
AL
Usala
I
I
Wexler
A
A
Posch
M K
MK
Gupta
D001323:Autoantibodies / Q000097:blood*; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000276:immunology*; D007074:Immunoglobulin G / Q000097:blood; D018828:Immunoglobulins, Thyroid-Stimulating; D007231:Infant, Newborn; D011247:Pregnancy; D011248:Pregnancy Complications / Q000276:immunology; D011297:Prenatal Exposure Delayed Effects; D011989:Receptors, Thyrotropin / Q000276:immunology*; D013960:Thyroid Function Tests; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000097:blood*
D001323:Autoantibodies; D007074:Immunoglobulin G; D018828:Immunoglobulins, Thyroid-Stimulating; D011989:Receptors, Thyrotropin; D013972:Thyrotropin; D013974:Thyroxine