From the Guidelines
Hyperthyroidism is a condition characterized by an overproduction of thyroid hormones, defined biochemically by a low or undetectable TSH level and an elevated T4 or T3 level.
Definition and Classification
- Hyperthyroidism can be classified into two categories: subclinical hyperthyroidism and overt hyperthyroidism.
- Subclinical hyperthyroidism is an asymptomatic condition with a serum TSH level below the lower threshold of a specified laboratory reference interval (usually 0.4 mIU/L) but normal T4 and triiodothyronine (T3) levels 1.
- Overt hyperthyroidism is defined biochemically by a low or undetectable TSH level and an elevated T4 or T3 level, and may or may not be associated with symptoms such as weight loss, heart palpitations, heat intolerance, and hyperactivity 1.
Symptoms and Diagnosis
- Symptoms of hyperthyroidism can be relatively nonspecific, including weight loss, heart palpitations, heat intolerance, and hyperactivity 1.
- The serum TSH test is the primary screening test for thyroid dysfunction, and multiple tests should be done over a 3- to 6-month interval to confirm or rule out abnormal findings 1.
Treatment and Management
- Hyperthyroidism is treated with antithyroid medications (such as methimazole) or nonreversible thyroid ablation therapy (for example, radioactive iodine or surgery) 1.
- Treatment is generally recommended for patients with a TSH level that is low or undetectable, and an elevated T4 or T3 level.
From the Research
Definition of Hyperthyroidism
- Hyperthyroidism is a condition where the thyroid gland produces and secretes inappropriately high amounts of thyroid hormone, leading to thyrotoxicosis 2.
- It is a pathological syndrome in which tissue is exposed to excessive amounts of circulating thyroid hormone 3.
- Hyperthyroidism is an excessive concentration of thyroid hormones in tissues caused by increased synthesis of thyroid hormones, excessive release of preformed thyroid hormones, or an endogenous or exogenous extrathyroidal source 4.
Causes of Hyperthyroidism
- The most common causes of hyperthyroidism are Graves' disease, toxic multinodular goiter, and toxic adenoma 2, 3, 4, 5, 6.
- Other causes include autoimmune postpartum and subacute thyroiditis, tumours that secrete thyrotropin, and drug-induced thyroid dysfunction 3.
- Thyroiditis, toxic multinodular goiter, toxic adenomas, and side effects of certain medications are also common causes of hyperthyroidism 6.
Diagnosis and Treatment
- The diagnosis of hyperthyroidism is generally straightforward, with raised serum thyroid hormones and suppressed serum thyrotropin in almost all cases 3.
- Treatment options for hyperthyroidism include anti-thyroid medications, radioactive iodine, and surgery 2, 3, 4, 5, 6.
- The choice of treatment depends on the underlying diagnosis, the presence of contraindications to a particular treatment modality, the severity of hyperthyroidism, and the patient's preference 4, 5, 6.
Symptoms and Complications
- Common symptoms of thyrotoxicosis include anxiety, insomnia, palpitations, unintentional weight loss, diarrhea, and heat intolerance 5.
- Untreated hyperthyroidism can cause cardiac arrhythmias, heart failure, osteoporosis, and adverse pregnancy outcomes 5.
- Hyperthyroidism may lead to unintentional weight loss and is associated with increased mortality 5.