Читать книгу A Practical Approach to Special Care in Dentistry - Группа авторов - Страница 239

 Primary hypothyroidism (due to thyroid hormone deficiency)May be related to iodine deficiency as iodine is a trace element essential for the synthesis of thyroid hormones, tri‐iodothyronine (T3) and thyroxine (T4)Iodine (as iodide) is found in the oceans; hence geographical areas that are iodine deficient tend to be inland and mountainous; more cases of congenital hypothyroidism (cretinism) are detected hereAutoimmune hypothyroidism (Hashimoto disease) is the most common cause in areas where there is sufficient iodine intakeDrugs can interfere with thyroid hormone production (e.g. amiodarone, lithium, some antiepileptic drugs, interferon‐alpha, some tyrosine kinase inhibitors)Iatrogenic causes include the administration of radioactive iodine to patients with hyperthyroidism, and those undergoing thyroid surgery or radiation therapy in the neckInfiltrative diseases which involve the thyroid gland may also be responsible (e.g. neoplasia)

 Secondary hypothyroidismCentral hypothyroidism: due to thyrotropin‐releasing hormone (TRH) deficiency or TSH deficiency and is associated with lesions in the hypothalamus and pituitary gland (mainly hypophysis adenoma), Sheehan syndrome, TRH resistance, radiation therapy to the brain and secondary to drugs such as dopamine, prednisone or opioidsFigure 5.2.3 Goitre (enlarged thyroid gland).Peripheral hypothyroidism: very uncommon and corresponds to an overexpression of deiodinase 3 (an enzyme that inactivates tyrosine) in patients with cancer and those with rare genetic syndromes