[Hypothyroidism-when and how to treat?]

Area of Science:

• Endocrinology
• Internal Medicine

Background:

• Hypothyroidism diagnosis relies on clinical presentation and thyroid-stimulating hormone (TSH) levels.
• Subclinical hypothyroidism presents with elevated TSH and normal free thyroxine (fT4) and triiodothyronine (fT3), while overt hypothyroidism shows reduced fT4 and fT3.

Purpose of the Study:

• To outline the diagnostic criteria and therapeutic approaches for hypothyroidism.
• To discuss the controversies and considerations in treating subclinical hypothyroidism and the standard of care for levothyroxine (T4) therapy.

Main Methods:

• Review of diagnostic markers including TSH, fT4, and fT3.
• Analysis of treatment guidelines for hypothyroidism, focusing on T4 monotherapy and considerations for combination therapy.

Main Results:

• Levothyroxine (T4) therapy initiation depends on TSH levels, patient age, pregnancy, and comorbidities.
• Thyroid hormone replacement is indicated for TSH >10 mU/l in non-pregnant adults ≤70 years.
• The goal of T4 replacement in primary hypothyroidism is a TSH level within the 0.4-4.0 mU/l reference range.

Conclusions:

• Standard hypothyroidism treatment involves T4 monotherapy with biochemical targets for TSH.
• Treatment of subclinical hypothyroidism is controversial, while secondary hypothyroidism management focuses on fT4 levels.
• Combination T4/T3 therapy is not standard but may be considered for persistent symptoms under expert guidance.