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.
Usala
A L
AL
Division of Pediatric Endocrinology and Metabolism, Rainbow Babies and Children's Hospital, Cleveland, Ohio.
Wexler
I
I
Posch
A
A
Gupta
M K
MK
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