الفهرس 
THYROID PHYSIOLOGYOnly 14 pages are availabe for public view
 |  | from | 250 |  |  |
| | | from | 250 | | |
Abstract
Autoimmune thyroid disease have been long known to ”run in amities”. They fit into the category of multifactorial genetic diseases. ~he genetic element in these disorders rarely manifests itself in all-or¬ on fashion as it does in the simply inherited (Mendelian) disorders and in chromosomal aberrations. Instead, it is the interaction of ’multiple genes with multiple environmental factors, that produces the familial aggregation, so there is a polygenic component consisting of a <series of genes that interact in a cumulative fashion . Multifactorial disorders are heterogeneous in the sense that the relative contribution of the polygenic factors ”risk genes” and environmental factors to the etiology vary greatly from patient to patient . However, it is important to remember that among common phenotypes which are largely multifactorial, often a small proportion will be created by major mutant genes . The hypothesis of a polygenic component in the inheritance of multifactorial diseases has been given a sound basis by the demonstration that at least one third of all gene loci harbor polymorphic alleles that vary among individuals. Such a large degree of variations in normal genes undoubtedly provides the substrate for variations in genetic predisposition with which environmental factors can interact, so far, the genetic loci most strikingly associated with predisposition to specific disease are those which constitute the HLA system.