September 1992

Elimination Kinetics of Maternally Derived Thyrotropin Receptor–Blocking Antibodies in a Newborn With Significant Thyrotropin Elevation

Author Affiliations

From the Division of Pediatric Endocrinology and Metabolism, Rainbow Babies and Children's Hospital, Cleveland, Ohio (Drs Usala and Wexler); the Department of Pediatrics, Case Western Reserve University School of Medicine, Cleveland (Drs Usala and Wexler); and the Department of Immunopathology, The Cleveland Clinic Foundation (Ms Posch and Dr Gupta). Dr Usala is currently with the Section of Pediatric Endocrinology, East Carolina University School of Medicine, Greenville, NC.

Am J Dis Child. 1992;146(9):1074-1077. doi:10.1001/archpedi.1992.02160210076025

• Objective.  —To determine the course of maternally derived elevations in thyrotropin-binding inhibitory immunoglobulins in a neonate.

Design.  —Case report.

Setting.  —University pediatric endocrinology clinic and endocrine immunology laboratory in Ohio.

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

Interventions.  —None.

Measurements/Main 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.(AJDC. 1992;146:1074-1077)