Carbamazepine (Tegretol) inhibits in vivo iodide uptake and hormone synthesis in rat thyroid glands
Decreased serum concentrations of T3 and T4 occur in patients treated with the anticonvulsant drug carbamazepine (CBZ), but with rare exception, these patients remain euthyroid. The mechanism that accounts for diminished hormone levels is unknown, and our objective was to study the direct effect of CBZ on iodide uptake and hormone synthesis in thyroid glands of CBZ-treated and pair-fed control rats. Chronic ingestion (per os) of CBZ in male rats reduced the four hour thyroid 131I-iodide uptake by approximately 60%. This inhibition occurred after the animals had received sufficient CBZ to attain plasma CBZ concentrations of 0.8 microgram/ml. Continued treatment with CBZ ranging from 560 to 800 mg/kg/day for 14 days did not result in further inhibition of iodide uptake even though the plasma CBZ concentrations had increased 6-20 fold. No inhibition of iodide uptake was apparent when the animals initially received CBZ ranging from 40 to 152 mg/kg body weight for 22 days when there were no detectable levels of plasma CBZ. Overall growth rates of CBZ-treated rats were slightly (6-10%) less than the pair-fed control animals. Plasma T4 concentrations were reduced by 18% (p less than 0.05) in the CBZ-fed animals, while T3 concentrations were diminished by 53% (p less than 0.01). CBZ appeared to alter thyroidal iodide transport because the thyroid:plasma iodide ratios were decreased by 26% in the drug-treated rats. The distribution of radioiodine in thyroidal iodoamino acids was essentially the same in both groups of rats but the absolute quantities of radioiodine were more than 2.5 times greater in the control rats. CBZ failed to inhibit peroxidase-catalyzed iodide and guaiacol oxidation in vitro.
- Research Organization:
- Univ. of California, San Diego (USA)
- OSTI ID:
- 7151619
- Journal Information:
- Endocr. Res.; (United States), Vol. 13:4
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ANTICONVULSANTS
BIOLOGICAL EFFECTS
IODINE 131
UPTAKE
THYROID
RADIONUCLIDE KINETICS
THYROID HORMONES
BIOSYNTHESIS
IN VIVO
INHIBITION
PATIENTS
RATS
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BODY
CENTRAL NERVOUS SYSTEM DEPRESSANTS
DAYS LIVING RADIOISOTOPES
DRUGS
ENDOCRINE GLANDS
GLANDS
HORMONES
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPES
MAMMALS
NUCLEI
ODD-EVEN NUCLEI
ORGANS
PEPTIDE HORMONES
RADIOISOTOPES
RODENTS
SYNTHESIS
VERTEBRATES
560162* - Radionuclide Effects
Kinetics
& Toxicology- Animals
Plants
Microorganisms
& Cells