Hyperthyroidism - Causes
Graves' Disease and other Causes of Hyperthyroidism
Graves' disease is an auto-immune disease which causes hyperthyroidism (also known as an overactive thyroid). The condition was named after Robert Graves, an Irish doctor, who first described the disease in 1835. Graves' disease is caused by abnormal antibodies that stimulate the thyroid to produce more thyroid hormone. The disease is diagnosed with a blood test which can detect thyroid stimulating antibodies (TSAb). The TSH (thyroid stimulating hormone) may be abnormally low or undetectable and the thyroid hormone levels may be raised.
Patients with hyperthyroidism have an increased metabolism and generally don't need much sleep. Yet initially they have boundless energy and are often quite ambitious. Despite increased food consumption many patients lose weight. They may develop anger management problems, mood disorders, anxiety, nervousness, and eventually they may feel exhausted. The disease can be insidious and destructive. Often personal relationships are affected and the performance at work may suffer as well.
Treatment consists of anti-thyroid drugs, radioactive iodine treatment or surgery. Many patients become hypothyroid after treatment.
Graves' disease can cause very high (toxic) thyroid hormone levels, which is referred to as thyrotoxicosis. A "thyroid storm" is a potentially life threatening complication of thyrotoxicosis which may be triggered by stress, surgery or illness. "Thyroid storm" can occur in people who are not treated for the disease or in people who cannot control their condition with treatment. Symptoms include chest pain, fever, fast heart beat, vomiting, shortness of breath or abdominal pain.
Toxic Multinodular Goitre & Toxic Solitary Thyroid Nodule
One nodule or multiple nodules in the thyroid gland start to produce thyroid hormone on their own, which may produce symptoms of hyperthyroidism. The pituitary gland responds to the excess level of thyroid hormone by reducing the TSH (thyroid stimulating hormone) as thyroid hormone levels start to rise, but the nodules don't respond to the TSH.
People diagnosed with a toxic multinodular goitre or a solitary thyroid nodule don't usually experience severe symptoms of hyperthyroidism and the nodules are not associated with the bulging eyes experienced by some patients with Graves' disease. People diagnosed with a solitary thyroid nodule have a higher incidence of thyroid cancer, compared to people diagnosed with a multinodular goitre. The thyroid hormone producing nodules come up as "hot" nodules on nuclear thyroid scans and are in fact hyperfunctioning benign thyroid tumours. Nodules that don't produce thyroid hormone appear as "cold" nodules on nuclear thyroid scans and are not active. The word "toxic" refers to very high levels of thyroid hormone produced by a nodule.
Subacute Granulomatous Thyroiditis - De Quervain's Thyroiditis
Subacute granulomatous thyroiditis is caused by a viral infection. The thyroid gland becomes inflamed and very painful. Patients may experience symptoms of hyperthyroidism followed by symptoms of hypothyroidism. Most people recover completely within a few weeks or a few months. It is thought that many viruses can cause subacute thyroiditis, like the Coxsackie virus or Epstein-Barr virus. The patient may experience a fever, pain in the neck area, jaw and ears. Some blood tests may be abnormal, such as the ESR (inflammation marker) and thyroglobulin may both be elevated. The 'radioactive iodine uptake count" is usually low.
Postpartum Thyroiditis - Silent Thyroiditis
Silent thyroiditis is painless and is believed to be a silent and temporary attack on the thyroid gland by the immune system. It commonly occurs in the postpartum period (within the year after childbirth) and may be misdiagnosed as postpartum depression. When the thyroid cells are being destroyed more thyroid hormone leaks into the blood, producing symptoms of mild hyperthyroidism, which can last a few weeks. In some cases it can last a few months. After the attack, the thyroid gland is unable to produce enough thyroid hormone for a few weeks or longer. The thyroid gland then starts to repair itself. This condition initially may be confused with Graves' disease.
A test, called "radioactive iodine uptake count", can help you with the correct diagnosis. A high count is indicative of Graves' disease and a low count is indicative of silent thyroiditis. Antimicrosomal antibodies (thyroid autoantibodies) are present in at least half the patients.
Drug Induced Hyperthyroidism
Amiodarone (a drug used to treat an irregular heartbeat) can cause an overactive thyroid (or underactive thyroid) and you should have your thyroid function checked regularly. This drug can come under the following names; Aratac, Cardinorm, Cordarone or Genrx amiodarone. Other drugs, especially drugs containing high amounts of iodine like amiodarone, can also cause thyroid dysfunction (either overactive thyroid or underactive thyroid).
A pituitary tumour may release too much TSH (thyroid stimulating hormone) which causes the thyroid to produce too much thyroid hormone, resulting in hyperthyroidism.
Copyright © 2011-2015 Monique Atkinson
Disclaimer The information provided is for educational purposes only and is not intended to be medical advice. The contents must not be relied upon in place of advice and treatment from a qualified medical practitioner. THYROID WA SUPPORT GROUP INC. and the author disclaim any liability whatsoever.