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Administrative data

endocrine system modulation
Type of information:
experimental study
Adequacy of study:
other information
3 (not reliable)
Rationale for reliability incl. deficiencies:
other: Documentation insufficient for assessment (no data on purity, no data on food consumption, i.e. on ADCA exposure, lack of data on animals and methods)

Data source

Reference Type:
Effect of Azodicarbonamide (1,1'-Azobisformamide) on Thyroid Function
Gafford FH, Sharry PM, Pittman JA
Bibliographic source:
Clin Endocrinol Metab. 1971, May; 32(5):659-62

Materials and methods

Test guideline
no guideline followed
GLP compliance:
Type of method:
in vivo
Endpoint addressed:
repeated dose toxicity: oral

Test material

Constituent 1
Chemical structure
Reference substance name:
EC Number:
EC Name:
Cas Number:
Molecular formula:
(E)-(carbamoylimino)urea; (Z)-(carbamoylimino)urea
Details on test material:
ADA (Azodicarbonamide) and BiU (Biurea)
Supplied by Aldrich Chemical-Company, Inc., Cedar Knolls, N. J.

Test animals

Details on test animals or test system and environmental conditions:
- Weight at study initiation: 160-180 g

Administration / exposure

Route of administration:
other: in diet and IP
other: in diet of propylene glycol (IP)
Details on exposure:
In diet: Rats were maintained on a low iodine diet (Remington, General Blochemicals Incorporated, Chagrin Falls. Ohio).
IP: The volume of propylene glycol injected was 0.1 ml/100 g body wt/day for both control and experimental groups.
Analytical verification of doses or concentrations:
not specified
Duration of treatment / exposure:
10 days or 4weeks
Frequency of treatment:
ad lib or daily
Post exposure period:
Doses / concentrationsopen allclose all
Doses / Concentrations:
1, 5 and 10% ADA
nominal in diet
in diet
Doses / Concentrations:
5 and 10% BiU
nominal in diet
in diet
Doses / Concentrations:
20. 2 and 0.2mg ADA/100 g body wy
nominal conc.
Doses / Concentrations:
20 and 2 mg BiU/100g body wt
nominal conc.
Control animals:
yes, concurrent vehicle
yes, plain diet
Details on study design:
One day prior to the end of each experiment 0.1 pCi of 125I in isotonic saline was given ip to each rat.
The following day all rats were sacrificed with ether anesthesia and their thyroids removed and weighed.


Twenty-four hr thyroidal radioiodine uptakes were determined by counting thyroids and standards in an automatic well counter (NuclearChicago).
PBIs on pooled group plasma samples were determined for some of the experiments (Techniccn AutoAnalyaer), Plasma TSH levels were also determined from these pooled group plasma samples by radioimmunoassay.
Positive control:
In one experiment, a positive control group received a low iodine diet containing 0.1 %methimazole (MMI).

Results and discussion

Any other information on results incl. tables

The ADA-treated-groups had thyroidal radioiodine uptakes which tended in all cases to be lower than the controls at dietary levels of 1, 5 and 10% ADA. The decrease was statistically significant in those groups which received 5 or 10% ADA in experiments lasting 10 days or 4 weeks. However, there was no concomitant thyroid enlargement, except in one experiment of one week's duration in which the total body weight of the test animals was significantly reduced by about 10%.

The latter effect contributed to the relative thyromegaly in the one treated group which showed goiter (the group receiving 10% ADA).


Thyroid weights per rat in this experiment (means ±SD) for the controls, 1% ADA and 10% ADA were 22.6 ±5.7, 26.0 ±3.2 and 28.0±7.6 mg, respectively. The possible goitrogenesis in the 10% ADA group in this experiment was not nearly so striking as that seen with methimazole administration, and in a 10-day 5% ADA group there was a slight but statistically significant reduction in thyroid weight.

In the 4-week, 10% ADA experiment there was no significant change in thyroid weight from control values. The serum protein bound iodine concentrations (PBI) on pooled samples tended to be lower in the test animals.

Oral administration of BiU at levels of 5 and 10% of the diet did not significantly alter thyroidal radioiodine uptakes after 1 week or 10 days, nor did goiter develop or PBI fall.


No significant alterations of thyroid uptake, thyroid weight, or plasma PBI were seen. A dose of 20 mgADA/100 g body wb/day killed 5 of 6 rats during the course of 1 week. No deaths occurred until day 3 of the experiment, and each was preceded by 24-48 hr of macroscopic hematuria. The mode of onset of these deaths indicated a possible cumulative toxicity of ADA when administered parenterally at high dose levels. Thyroid function data on the 3 surviving rats appeared similar to control values. However, reduction of the dose of ADA by factors of 10 and 100 eliminated all systemic signs of toxicity (anorexia, weight loss and gross hematuria) and gave clear evidence of thyroid function similar to controls, as did BiU in doses of 2 and 20 mg/100 g body wt/day. Plasma TSH levels were determined on pooled samples for which PBI data are also shown, and the plasma TSH did not rise significantly (remained below the limit of detectability, 80 µU/ml).

Thus, ADA, given as 5 or 10% of the diet for 10 or 28 days, was found to weakly inhibit thyroidal radioiodine uptake. The magnitude of this effect was much smaller and less consistent than the depression of uptakes seen with administration of potent antithyroid agents such as methimazole (MMI), propylthiouracil (P'TIJ), or aminotriazole (ATZ).

Inhibition of uptake by ADA occurred only at dose levels much higher than the minimal effective doses of MMI, PTU, or ATZ. Although there was a tendency to reduced serum PBIs in the ADA groups, this was not marked, and direct estimates of serum TSH showed no increase. There was no consistent goitrogenesis, and the mechanism for the reduction in thyroidal radioiodine uptake by ADA is not established. Depression of the 24-hr uptake is an earlier and more sensitive measure of antithyroid activity than increased serum TSH, goiter formation, or decreased PBI, and the most likely explanation for the reduced uptakes seen in these studies is that ADA does in fact have a weak antithyroid action.

Although many extrathyroid factors can affect the uptake (stress, renal insufficiency, cardiac decompensation, changes in fecal bulk, altered stable iodine intake, etc.), no evidence of any of these was observed in the present experiments, and the rats appeared clinically healthy while receiving the diet containing 10% ADA.

There was no evidence that BiU altered thyroid function in any way.

The apparent antithyroid effect of ADA in these experiments is of no significance in relation to its use in the baked goods industry. For example, at the highest permissible level of use (45 ppm), bread containing 75% flour would have only 33.75 mg ADA/kg of bread; and the minimal effective dose of ADA needed to depress thyroid uptake in the rat was 50 g/kg of rat chow. In addition, ADA is converted to BiU when water is added to the flour, and further conversion occurs when the temperature in the baking oven exceeds 180 C. Thus, the question of antithyroid activity of ADA is now of interest only in connection with a possible structure-activity relation to known antithyroid agents. These' experiments show that there would be no ill effects from any such antithyroid activity of ADA in the quantities in which it is used commercially.

Applicant's summary and conclusion