Thyroid hormones which causes the thyroid to enlarge (the resulting medical condition is called "endemic colloid goitre"; see goitre). This has the effect of increasing the thyroid's ability to trap more iodide, compensating for the iodine deficiency and allowing it to produce adequate amounts of thyroid hormone. Most of the thyroid hormone circulating in the blood is bound to "transport protein"s. Only a very small fraction of the circulating hormone is free (unbound) and biologically active, hence measuring concentrations of free thyroid hormones is of great diagnostic value. When thyroid hormone is bound, it is not active, so the amount of free
Zinc deficiency deficiency is rare, and is mainly seen in persons with acrodermatitis enteropathica, a severe defect in zinc absorption due to a congenital deficiency in the zinc carrier protein ZIP4 in the enterocyte. Mild zinc deficiency due to reduced dietary intake is common. Conservative estimates suggest that 25% of the world's population is at risk of zinc deficiency. Zinc deficiency is thought to be a leading cause of infant mortality. Providing micronutrients, including zinc, to humans is one of the four solutions to major global problems identified in the Copenhagen Consensus from an international panel of economists. Significant historical events related