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
DNA repair-deficiency disorder DNA repair-deficiency disorder A DNA repair-deficiency disorder is a medical condition due to reduced functionality of DNA repair. DNA repair defects can cause an accelerated aging disease or an increased risk of cancer, or sometimes both. DNA repair defects are seen in nearly all of the diseases described as accelerated aging disease, in which various tissues, organs or systems of the human body age prematurely. Because the accelerated aging diseases display different aspects of aging, but never every aspect, they are often called segmental progerias by biogerontologists. Some examples of DNA repair defects causing progeroid syndromes in humans or mice