Familial dysalbuminemic hyperthyroxinemia in pregnancy
1Mt Sinai Services at Queens Hospital Center, Jamaica, New York, USA.
European Journal of Endocrinology
|December 1, 1995
Summary
Familial dysalbuminemic hyperthyroxinemia (FDH) can complicate pregnancy diagnosis. This condition involves increased thyroid hormone binding to albumin, mimicking thyrotoxicosis but requiring distinct management.
Area of Science:
- Endocrinology
- Genetics
- Obstetrics
Background:
- Thyroid hormone regulation during pregnancy is complex, with physiological changes potentially masking or mimicking thyroid dysfunction.
- Thyroid-stimulating hormone (TSH) levels are typically suppressed in the first trimester of pregnancy.
- Familial dysalbuminemic hyperthyroxinemia (FDH) is a genetic disorder characterized by abnormal binding of thyroxine (T4) to albumin.
Observation:
- A 16-year-old pregnant woman presented with goiter and elevated total T4 and T3 levels, yet normal TSH.
- Initial assessment suggested TSH-producing pituitary adenoma or generalized thyroid hormone resistance.
- Analysis revealed increased T4 binding to albumin in the patient, her mother, and her infant, characteristic of FDH.
Findings:
- The free T4 estimate was artifactually elevated due to FDH albumin's increased affinity for the assay analog.
- Pregnancy further increased T3 and T4 concentrations, with FDH exacerbating T4 elevation.
- This case represents the first report of FDH diagnosed during pregnancy.
Implications:
- Diagnosing FDH during pregnancy is challenging due to overlapping hormonal changes.
- Distinguishing FDH from true thyrotoxicosis is crucial for appropriate maternal and fetal health.
- Inappropriate treatment for presumed thyrotoxicosis in FDH can adversely affect fetal development.
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