ABSTRACT
The purpose of this study was to determine the effects of nitrate on both the activity of the thyroid gland and other biological parameters. After 5-month treatment, nitrate 150 and 500 mg/l induced a significant decrease in the serum level of thyroid hormone T3. For T4, the 500 mg/l dose only reduced its plasma level. On the other hand, nitrate induced a dose-dependent increase in the weight of the thyroid gland. The histological study of the thyroid gland shows vacuolisation and an increase in the size of the follicles accompanied by a flatness of follicular epithelium with nitrate 150 and 500 mg/l. We concluded that the presence of high concentrations of nitrate in drinking water influence the growth, induce morpho-functional modifications of the thyroid gland and might be considered as a goitrigenic factor.
Subject(s)
Nitrates/toxicity , Potassium Compounds/toxicity , Thyroid Gland/drug effects , Water Pollutants/toxicity , Administration, Oral , Animals , Dose-Response Relationship, Drug , Drinking , Male , Morocco , Nitrates/administration & dosage , Potassium Compounds/administration & dosage , Rats , Rats, Wistar , Thyroid Gland/metabolism , Thyroid Gland/pathology , Thyroxine/blood , Triiodothyronine/blood , Water Pollutants/administration & dosage , Water Supply/analysisABSTRACT
Endemic goiter in Morocco is localized in the Rif and Atlas mountains. In this study, performed in the Skoura-Toundoute areas (high Atlas), we demonstrate that iodine deficiency is the main factor involved in the development of endemic goiter. However it may not constitute the only etiological factor. The median urinary iodine excretion, measured on untimed samples, was low both in goitrous patients, m = 18 micrograms/l (n = 109) and in non goitrous subjects, m = 24 micrograms/l (n = 47). The value found in a nonendemic region (Casablanca) was much higher m = 117 micrograms/l (n = 67). Another approach to evaluate iodine intake per day was the analysis of iodine content of some samples of cereals (barley, wheat and corn), drinking water, sea and rock salt, cow and breast milk. Iodine content is low, specially in the endemic area: barley = 90 micrograms/kg (n = 1); wheat = 227 micrograms/kg (n = 1); corn = 91 micrograms/kg (n = 1); water = 0.92 to 1.30 micrograms/l (n = 3); cow milk = 6 to 33 micrograms/l (n = 10) breast milk = 10 to 55 micrograms/l (n = 14); rock salt = 420 to 660 micrograms/kg (n = 8); sea salt = 90 to 160 micrograms/kg (n = 4). Sodium chloride intake per day, estimated by the measurement of sodium and chloride urinary excretion, is normal both in the Skoura-Toundoute areas (10.7 g and 9.8 g for goitrous and nongoitrous subjects, respectively) and in Casablanca (10.9 g for control persons). Altogether the results demonstrate the importance of introducing the practice of iodinated salt in the prophylaxis of endemic goiter in this area.
