Subclinical hypothyroidism and subclinical hyperthyroidism

Abstract

Subclinical thyroid dysfunction occurs when peripheral thyroid hormone levels are within the normal laboratory reference range and the serum thyroid-stimulating hormone (TSH or thyrotropin) level is greater than normal (subclinical hypothyroidism) or less than normal (subclinical hyperthyroidism; TSH normal laboratory reference range: 0.3–5.0 mIU/l). For patients with subclinical hypothyroidism (serum TSH levels >10 mIU/l), thyroxine therapy is prescribed if other causes of TSH elevation and transient conditions have been excluded. For serum TSH levels between 5.0 and 10.0 mIU/l, selective therapy should be considered. For patients with sustained subclinical hyperthyroidism (serum TSH levels <0.1 mIU/l), therapy is recommended, especially in older patients. Observation or selective therapy should be considered for patients with serum TSH levels between 0.1 and 0.3 mIU/l.

Keywords::

• antithyroid antibody
• cardiac risk factor
• hyperthyroidism
• hypothyroidism
• subclinical hyperthyroidism
• subclinical hypothyroidism
• thyroid-stimulating hormone screening
• thyrotropin
• thyroxine therapy

Financial & competing interests disclosure

The author has no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.

Notes

TSH: Thyroid-stimulating hormone.

Data from [17–19].

AACE: American Association of Clinical Endocrinologists; NACB: National Academy of Clinical Biochemistry; NHANES: National Health and Nutrition Examination Survey.

TSH: Thyroid-stimulating hormone.

TSH: Thyroid-stimulating hormone.

Modified from [31].

^†TSH levels higher than 8.0 mIU/l increase the likelihood of progression to TSH higher than 10.0 mIU/l in 3 years [Fatourechi et al., unpublished data (2003)].

^‡Down syndrome patients are at high risk of progression to overt hypothyroidism.

TSH: Thyroid-stimulating hormone.