History and Objectives: Considering recent reports on the goitrogenic effect of Magnesium and the effect of iodine on thyroid gland, the present study was carried out in order to investigate the effect of the Magnesium alone and Magnesium alone with Iodine on the activity of thyroid gland on white rat in Ahwaz Medical University.

Materials and Methods: An experimental study on 73 rat was conducted. Animals were divided into 3 groups: Control (25 rat), Magnesium group (One gram of Magnesium is given per kilogram food (24 rat) and Iodine-Magnesium group (24 rat). Food was given in the form of pellet. The effect of Magnesium alone and along with Iodine was studied by determination of T3, T4, TSH and T3Uptake (Radioimmunoassay) at the 1.5 and 3.5 month of nutritional supplementation.

Results: Blood level of T3 and TSH did not give significant difference in 3 groups. TSH levels in Magnesium group (5.3±0.2 uIU/dl) showed 20% increase compared to the control group (4.4±1.2 uIU/dl, P<0.05) however there no significant difference between Magnesium-Iodine group compared to the control group. T3Uptake levels in the control group (48.6%±0.6) was 9% higher compared to the Magnesium group (44.3%±0.5, P<0.0002) and in the Magnesium-Iodine group was 42.1%±1.2 which had a 13% reduction compared to the control group (P<0.0001).

Conclusion: These findings indicate that Magnesium does not have goitrogenic effect however further histological analysis as to the influence of Magnesium on the thyroid gland is suggested.