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Hyperthyroidism and thyrotoxicosis: Difference between revisions
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'''Thyrotoxicosis''' or hyperthyroxinaemia is the state where the level of circulating free T3 and T4 is elevated, causing hypermetabolism. It is most commonly caused by '''hyperthyroidism''', which is the state where the thyroid is overactive, | <section begin="clinical biochemistry" />'''Thyrotoxicosis''' or hyperthyroxinaemia is the state where the level of circulating free T3 and T4 is elevated, causing hypermetabolism. It is most commonly caused by '''hyperthyroidism''', which is the state where the thyroid is overactive. However, thyrotoxicosis can also be caused by ectopic hormones or destruction of the thyroid. Because the most common cause of thyrotoxicosis is hyperthyroidism, the two terms are often used interchangeably. | ||
== Etiology == | == Etiology == | ||
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** TSH-producing pituitary adenoma | ** TSH-producing pituitary adenoma | ||
In regions without [[iodine deficiency]], Graves disease is the most common cause of thyrotoxicosis. In iodine deficient regions, toxic adenoma and toxic multinodular goitre are more common. | In regions without [[iodine deficiency]], Graves disease is the most common cause of thyrotoxicosis. In iodine deficient regions, toxic adenoma and toxic multinodular goitre are more common.<section end="clinical biochemistry" /> | ||
== Clinical features == | == Clinical features == | ||
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* Fine tremor | * Fine tremor | ||
* Anxiety, restlessness | * Anxiety, restlessness | ||
<section begin="clinical biochemistry" /> | |||
== Diagnosis and evaluation == | == Diagnosis and evaluation == | ||
The diagnosis of (primary) hyperthyroidism is based on the levels of [[TSH]], the most sensitive biomarker. Free T4 and T3 are measured to look for subclinical hyperthyroidism. | The diagnosis of (primary) hyperthyroidism is based on the levels of [[TSH]], the most sensitive biomarker. Free T4 and T3 are measured to look for subclinical hyperthyroidism. | ||
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* Autoantibodies against thyroid peroxidase (anti-TPO), thyroglobulin (anti-Tg), and TSH receptor (anti-TSHR) | * Autoantibodies against thyroid peroxidase (anti-TPO), thyroglobulin (anti-Tg), and TSH receptor (anti-TSHR) | ||
** Anti-TPO and elevated in autoimmune thyroiditis | |||
** Anti-thyroglobulin may also be used in autoimmune thyroiditis, but is less sensitive and specific than anti-TPO, so anti-TPO is used instead | |||
** Anti-TSHR is elevated in Graves disease | |||
* [[Ultrasound]] | * [[Ultrasound]] | ||
* Thyroid [[scintigraphy]] (nuclear imaging) | * Thyroid [[scintigraphy]] (nuclear imaging) | ||
<section end="clinical biochemistry" /> | |||
== Treatment == | == Treatment == | ||
Specific treatment depends on the underlying etiology, but supportive treatment is also available. [[Beta blocker|Beta blockers]] can be used, of which propranolol is the first choice as it inhibits conversion of T3 to T4. Benzodiazepines may also be used in very short courses for anxiety. | Specific treatment depends on the underlying etiology, but supportive treatment is also available. [[Beta blocker|Beta blockers]] can be used, of which propranolol is the first choice as it inhibits conversion of T3 to T4. Benzodiazepines may also be used in very short courses for anxiety. | ||