![]() NB: although these symptoms may be present, the symptoms and signs can be variable and in some patients they are very mild. Lid lag (may be present in any cause of hyperthyroidism).Proximal myopathy (muscle weakness ± wasting).Tachycardia - may be atrial fibrillation and/or heart failure (common in the elderly).Mental illness: may range from anxiety to psychosis.Weight loss despite an increased appetite.People with a history of other autoimmune disorders, those with a family history of thyroid or other autoimmune disorders and smokers are at an increased risk of developing Graves' disease. Three gene regions consistently linked to Graves' hyperthyroidism are the human leukocyte antigen region, CTLA4 and PTPN22, all of which encode proteins that are involved in immune function and linked to the cause of other autoimmune disorders. Highly active antiretroviral therapy (HAART).Toxic multinodular goitre (which is especially associated with an increased iodine intake, either from a change in diet or an acute dose from iodine-containing agents (eg, amiodarone, contrast agents)).Trauma to the thyroid gland (including surgery).Smoking (particularly for thyroid-associated ophthalmopathy).Other causes include exogenous thyroid hormone excess, drug-induced hyperthyroidism, TSH-secreting pituitary adenomas and pituitary resistance to thyroid hormones.Thyroiditis, in which destruction of thyroid cells causes release of thyroid hormones into the circulation, is implicated in about 10% of thyrotoxicosis cases.Thyrotoxicosis due to toxic nodular goitre is more common in people aged over 60 years.Graves' disease is the most common cause of thyrotoxicosis.Graves' disease is a rare disease in children, accounting for 1-5% of all patients with Graves' disease. Graves' disease accounts for around 75% of cases. Graves' disease In adults affects approximately 2% of women and 0.2% of men.Thyrotoxicosis is still under-diagnosed however - it has been shown that in people older than 65 years, undiagnosed hyperthyroidism occurs in 0.3% of people and around 2% of people aged over 65 years have subclinical hyperthyroidism.In Europe, thyrotoxicosis affects around 1 in 2,000 people annually.Free thyroid hormones in the circulation act negatively on the hypothalamus and pituitary - thus reducing the release of TRH and TSH.Most T3 and T4 in the circulation are bound to protein (mostly thyroglobulin) it is only free thyroid hormone that is active.T4 is inactive and needs to be converted to T3 - which occurs peripherally (such as in the liver and kidney).Greater amounts of T4 are produced than T3. The thyroid gland, in response to TSH, produces thyroxine (T4) and triiodothyronine (T3).TSH is released by thyrotropin-releasing hormone (TRH) from the hypothalamus.It is stimulated and controlled by TSH from the anterior pituitary. ![]() The thyroid gland is situated in the neck and its hormones control the metabolic rate of tissues.Anatomy and physiology of the thyroid gland
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