At the beginning of the 20th century, René Le Fort mapped typical locations for facial fractures; these are now known as Le Fort I, II, and III fractures (right). Le Fort I fractures, also called Guérin or horizontal maxillary fractures, involve the maxilla, separating it from the palate. Le Fort II fractures, also called pyramidal fractures of the maxilla, cross the nasal bones and the orbital rim. Le Fort III fractures, also called craniofacial disjunction and transverse facial fractures, cross the front of the maxilla and involve the lacrimal bone, the lamina papyracea, and the orbital floor, and often involve the ethmoid bone, are the most serious. Le Fort fractures, which account for 10–20% of facial fractures, are often associated with other serious injuries. Le Fort made his classifications based on work with cadaver skulls, and the classification system has been criticized as imprecise and simplistic since most midface fractures involve a combination of Le Fort fractures. Although most facial fractures do not follow the patterns described by Le Fort precisely, the system is still used to categorize injuries. Prevention
Measures to reduce facial trauma include laws enforcing seat belt use and public education to increase awareness about the importance of seat belts and motorcycle helmets. Efforts to reduce drunk driving are other preventative measures; changes to laws and their enforcement have been proposed, as well as changes to societal attitudes toward the activity. Information obtained from biomechanics studies can be used to design automobiles with a view toward preventing facial injuries.
Any abnormalities in this chain can result in thyroid hormone resistance and it has not been as well studied as the various forms of insulin resistance.The most well known cause of the syndrome are mutations of the β (beta) form (THRB gene) of the thyroid hormone receptor, of which over 100 different mutations have been documented. Mutations in MCT8 and SECISBP2 have also been associated with this condition. Regulation of thyroid hormone secretion
Hypothalamus secretes a hormone called thyrotropin releasing hormone (TRH) which in turn release thyroid stimulating hormone (TSH). TSH signals thyroid to secrete thyroid hormones thyroxine (T4) and triiodothyronine (T3). T4 gets converted to active T3 in peripheral tissues with the help of deiodinase enzymes. T3 negatively feedback on the pituitary and decreases TSH secretion. Diagnosis
The characteristic blood test results for this disorder can also be found in other disorders (for example TSH-oma (pituitary adenoma), or other pituitary disorders). The diagnosis may involve identifying a mutation of the thyroid receptor, which is present in approximately 85% of cases. Management
Beta blockers, like metoprolol, are sometimes used to help suppress symptoms. Incidence
Thyroid hormone resistance syndrome is rare, incidence is variously quoted as 1 in 50,000 or 1 in 40,000 live births. More than 1000 individuals have been identified with thyroid hormone resistance, of which 85% had thyroid hormone beta receptor mutation. References


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