Treatment of subclinical hypothyroidism: assessing when treatment is likely to be beneficial

ABSTRACT

Introduction: Subclinical hypothyroidism (SCH) is a common condition diagnosed in up to 16% of the population. SCH is diagnosed when serum TSH is high and circulating thyroid hormones are within the reference range. SCH is considered to be a mild form of thyroid failure by some due to the log-linear relationship between TSH and thyroid hormones. Nevertheless, it is unclear whether the treatment of SCH with thyroid hormones is beneficial, and hence, it is not surprising that expert opinions and recommendations from societies differ in their opinions on how best to manage SCH.

Areas covered: This article reviews the currently available evidence pertaining to SCH and provides recommendations as to when treatment of SCH should be considered. An electronic search of PubMed from 1970 to 2019 was performed and systematically reviewed studies assessing the effects of treatment in SCH. The main areas that are considered are the effects of treatment on symptoms and quality of life, and important clinical consequences including psychocognitive outcomes and cardiovascular events.

Expert opinion: Treatment of SCH with thyroid hormones is debated and the current literature in this area lacks clarity. We provide an evidence-based recommendation for when treatment of SCH with thyroid hormones should be considered.

KEYWORDS:

• Cardiovascular disease
• depression
• fatigue
• levothyroxine
• pregnancy
• psychocognitive symptoms
• subclinical hypothyroidism
• treatment
• weight
• children

Article highlights

• Subclinical hypothyroidism (SCH) is diagnosed when serum TSH levels are higher than the reference range and thyroid hormones are normal.

• SCH affects 5 – 16% of the adult population and is more common in older people and in women.

• Most children and older individuals with mild SCH (TSH<10.0 mIU/L) do not require treatment.

• Treatment should be considered in younger persons with SCH particularly if they have symptoms consistent with hypothyroidism, have a high risk of cardiovascular disease, or if serum TSH levels are consistently >10.0 mIU/L.

• Pregnant women with TSH levels above the semester-specific range and positive antibody to thyroid peroxidase (TPOAb) should be treated.

Declaration of interest

S Razvi has received speaker fees from Merck plc, Berlin Chemie plc, and Abbott India Pharmaceuticals Pvt Ltd. The authors have no other 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 apart from those disclosed.

Reviewer disclosures

A reviewer on this manuscript has disclosed that they were a member of the BMJ guideline about the use of levothyroxine for subclinical hypothyroidism, and also a member of American Association Guideline Committee. Peer reviewers on this manuscript have no other relevant financial relationships or otherwise to disclose.

Additional information

Funding

This paper was not funded.