Effect of concurrent vitamin A and iodine deficiencies on the thyroid-pituitary axis in rats

OBJECTIVE: Deficiencies of vitamin A and iodine are common in many developing countries. Vitamin A deficiency (VAD) may adversely affect thyroid metabolism. The study aim was to investigate the effects of concurrent vitamin A and iodine deficiencies on the thyroid-pituitary axis in rats. DESIGN: Weanling rats (n = 56) were fed diets deficient in vitamin A (VAD group), iodine (ID group), vitamin A and iodine (VAD + ID group), or sufficient in both vitamin A and iodine (control) for 30 days in a pair-fed design. Serum retinol (SR), thyroid hormones (FT(4), TT(4), FT(3), and TT(3)), serum thyrotropin (TSH), pituitary TSHbeta mRNA expression levels, and thyroid weights were determined at the end of the depletion period. MAIN OUTCOME: Compared to the control and ID groups, SR concentrations were about 35% lower in the VAD and VAD + ID groups (p < 0.001), indicating moderate VA deficiency. Comparing the VAD and control groups, there were no significant differences in TSH, TSHbeta mRNA, thyroid weight, or thyroid hormone levels. Compared to the control group, serum TSH, TSHbeta mRNA, and thyroid weight were higher (p < 0.05), and FT4 and TT4 were lower (p < 0.001), in the VAD + ID and ID groups. Compared to the ID group, TSH, TSHbeta mRNA, and thyroid weight were higher (p < 0.01) and FT(4) and TT(4) were lower (p < 0.001) in the VAD + ID group. There were no significant differences in TT3 or FT3 concentrations among groups. CONCLUSION: Moderate VAD alone has no measurable effect on the pituitary-thyroid axis. Concurrent ID and VAD produce more severe primary hypothyroidism than ID alone

Analysis of iodine and selenium trace elements in umbilical cord blood in cretinous regions in northwest China in 1999

Shaanxi Province located at Midwest inland of China was a typical iodine deficient disorders region. To investigate iodine and selenium levels of neonates in the Shaanxi sub-clinical cretinism region of China after supplement of iodine salt for nearly twenty years. We collected 56 umbilical cord blood samples from cretinous regions of Yijun County (a selenium deficient region) north of Shaanxi Province and Ziyang County (a selenium-enriched region) south of the province and from Lintong in Xi'an (a non-cretinous region for control). Among these samples 17 were collected from Ziyang, 20 from Lintong and 19 from Yijun. Seven trace elements of iodine, selenium, zinc, copper, iron, calcium and magnesium in the umbilical cord blood samples were measured and the results were processed statistically. There were no significant differences in the levels of iodine among all three counties. However, the level of selenium in Ziyang was the highest and in Yijun it was the lowest. The other trace elements such as Cu Zn Fe and Mg showed no significant difference among the three counties except for the Ca level which was lower in Yijun