<h2 style="color:#fe369c">Subclinical hyperthyroidism</h2>
Subclinical hyperthyroidism occurs when TSH is persistently low (suppressed) but thyroid hormone levels remain normal. It is considered a mild form of hyperthyroidism.1
What causes subclinical hyperthyroidism?
The most common cause of subclinical hyperthyroidism is excessive thyroid hormone replacement therapy.1,2
Other causes include1,2
Subclinical hyperthyroidism is often asymptomatic. However, some people may experience symptoms that are similar to hyperthyroidism, including:3
Subclinical hyperthyroidism is diagnosed through blood tests that measure thyroid function. The main thyroid hormones that are checked are TSH and T4. Before making a diagnosis of subclinical hyperthyroidism, your doctor may order additional tests to rule out other conditions that may result in low TSH levels.3
<p style="color:#000000">Tell your doctor if you notice any symptoms to get a proper diagnosis.</p>
Some patients with subclinical hyperthyroidism develop full-blown (overt) hyperthyroidism while in others, thyroid function may return to normal, depending on the cause.
The risk of progressing to overt disease varies depending on the underlying cause and the degree of TSH suppression. Progression is more likely if a person has a higher degree of TSH suppression and if there is a persistent underlying cause such as Graves’ disease or toxic thyroid nodule.3
Treatment may involve regular monitoring or starting on anti-thyroid medications. In some cases, surgery or radioactive iodine therapy may be required.1
If you have subclinical hyperthyroidism because of excessive thyroid hormone therapy, your doctor will adjust the dose of the medication to bring your TSH levels back to normal.4
<h2 style="color:#fe369c">Subclinical hypothyroidism</h2>
Subclinical hypothyroidism is a mild form of hypothyroidism that occurs when a person has persistent high TSH but normal thyroid hormone levels.5
The same conditions that cause overt or full-blown hypothyroidism can cause subclinical hypothyroidism. The most common cause is Hashimoto’s thyroiditis . Other causes include:3
Subclinical hypothyroidism is frequently asymptomatic especially in elderly patients. Some patients may experience non-specific symptoms, such as:1
Subclinical hypothyroidism is diagnosed based on blood tests for TSH and T4 levels, similar to the diagnosis of subclinical hypothyroidism. Your doctor will recheck your TSH levels within 3‒6 months to confirm your diagnosis.3
Subclinical hypothyroidism may go away on its own or progress to overt hypothyroidism. Progression to overt disease is more likely in people who have a higher degree of TSH elevation and if there is a persistent underlying cause such as Hashimoto’s thyroiditis.3
Treatment involves taking a low dose of thyroid hormone therapy called levothyroxine. Alternatively, your doctor may recommend a “wait and see” approach, with regular follow-ups to monitor your TSH levels.1
1. Kek PC, Ho SC, Khoo DH. Subclinical thyroid disease. Singapore Med J. 2003; 44: 595-600.
2. Palacios SS, Pascual-CorralesE, Galofre JC. Management of subclinical hyperthyroidism. Int J Endocrinol Metab. 2012; 10: 490-6.
3. Ng MCW, Loo WX, Poon ZM. Subclinical thyroid disorders: clinical significance and when to treat? PoSH.2014; 23: 226-40.
4. Wilson GR, Curry RW. Subclinical thyroid disease. Am Fam Physician 2005; 72: 1517-24.
5. Tng EL. The debate on treating subclinical hypothyroidism. Singapore Med J. 2016; 57: 539-45.
