TABLE E-1 Effects of Fluoride on Thyroid Follicular Cell Function in Experimental Animals

Species and Strain

Exposure Conditions

Fluoride Concentration or Dosea

Exposure Duration



Rats (Hebrew University albino, males; infants at start, 30-32 g)

See also Table E-16

Drinking water

0.55, 1, or 10 mg/L (0.055, 0.1, and 1 mg/kg/day)b

9 months

No significant differences in basal metabolic ratio, thyroid weight, radioiodine uptake, total blood iodine, protein-bound iodine, or urinary excretion.

TSH not measured.

Gedalia et al. 1960

Rats (females, 180-230 g)

Gastric tube 0.2 or 2.2 µg/day iodine in diet

750 µg/day in 1 mL water (3.3-4.2 mg/kg/day)

2 months

No effect of fluoride on body weight, weight of thyroid, total composition of iodinated amino acids, or amount of iodide present in the thyroid. No effect of fluoride on iodine excretion in the higher-iodine group.

Decreased protein-bound iodine, T3, and T4 (low-iodine group).

Decreased biogenesis of T3 and T4 following administration of131I (low- and high-iodine groups).

TSH not measured.

Stolc and Podoba 1960

Rats (Wistar, males; initial weight 170-230 g; 13 per group)

Drinking water Dietary iodine, 0.45 µg/g feed (0.45 ppm)

0, 0.1, or 1 mg/day (0, 0.43-0.59, or 4.3- 5.9 mg/kg/day)

60 days

Decreased plasma T3 and T4, decreased free T4 index, increased T3-resin uptake (all changes statistically significant except for the decrease in T3 for the group receiving 0.1 mg/day)c

TSH not measured.

Bobek et al. 1976

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