When to treat a patient for hypothyroidism (underactive thyroid gland)?

From the Guidelines

Treatment for hypothyroidism should be initiated when a patient has a TSH level greater than 10.0 mIU/L, as this is generally considered the threshold for initiation of treatment, based on expert opinion 1. When considering treatment for hypothyroidism, it is essential to evaluate the patient's TSH levels and symptoms.

• For patients with TSH levels between 4.5 and 10.0 mIU/L, the decision to start therapy is more controversial, and treatment is not routinely recommended, but thyroid function tests should be repeated at 6- to 12-month intervals to monitor for improvement or worsening in TSH level 1.
• The standard treatment for hypothyroidism is levothyroxine (synthetic T4), which helps to restore normal metabolism and prevent complications like cardiovascular disease, infertility, and myxedema coma.
• The initial dose of levothyroxine typically starts at 1.6 mcg/kg/day for otherwise healthy adults, though lower doses (25-50 mcg/day) are recommended for elderly patients or those with cardiac disease.
• TSH levels should be checked 6-8 weeks after starting treatment or changing doses, with a target TSH of 0.5-2.5 mIU/L for most adults.
• Levothyroxine should be taken on an empty stomach, 30-60 minutes before breakfast or 3-4 hours after the last meal of the day, and separated from medications that can interfere with absorption like calcium, iron supplements, and proton pump inhibitors.
• Treatment is typically lifelong for most causes of hypothyroidism, as the medication replaces the thyroid hormone the body cannot produce in sufficient quantities. The primary goal of treatment is to improve morbidity, mortality, and quality of life by restoring normal thyroid function, and this should be prioritized when making treatment decisions 1.

From the FDA Drug Label

Thyroid hormone drugs are indicated: As replacement or supplemental therapy in patients with hypothyroidism of any etiology, except transient hypothyroidism during the recovery phase of subacute thyroiditis Patients with hypothyroidism of any etiology, except transient hypothyroidism during the recovery phase of subacute thyroiditis, should be treated with thyroid hormone drugs, such as liothyronine (PO) 2.

• Primary hypothyroidism resulting from functional deficiency, primary atrophy, partial or total absence of thyroid gland, or the effects of surgery, radiation, or drugs, with or without the presence of goiter
• Secondary (pituitary) or tertiary (hypothalamic) hypothyroidism Key considerations for treatment include the etiology of the hypothyroidism and the presence of any underlying conditions, such as goiter or thyroid nodules.

From the Research

Treatment of Hypothyroidism

• The treatment of hypothyroidism is based on clinical signs and symptoms, as well as measurement of thyroid-stimulating hormone (TSH) concentration 3.
• Levothyroxine (T4) therapy is the standard of care for treatment of hypothyroidism, with the goal of achieving a TSH level within the reference range (0.4-4.0 mU/l) 3.
• The initiation of T4 therapy depends on the level of TSH elevation, as well as other factors such as patient age, presence of pregnancy or comorbidities 3.

Subclinical Hypothyroidism

• Subclinical hypothyroidism is characterized by elevated TSH with normal serum free thyroxine (fT4) and triiodothyronine (fT3) levels 3.
• Treatment of subclinical hypothyroidism is still a controversial topic, with some studies suggesting that treatment is not necessary unless the TSH exceeds 7.0-10 mIU/L 4, 5, 6.
• Patients with subclinical hypothyroidism and a TSH level greater than 10 mIU/L may benefit from treatment with levothyroxine 4, 5, 6.

Special Considerations

• In patients over 60 years or with known or suspected ischemic heart disease, levothyroxine therapy should be started at a lower dosage (12.5 to 50 mcg per day) 5.
• Women with hypothyroidism who become pregnant should increase their weekly dosage of levothyroxine by 30% up to nine doses per week 5.
• Patients with persistent symptoms after adequate levothyroxine dosing should be reassessed for other causes or the need for referral 5.

Alternative Therapies

• Combination therapy with levothyroxine and liothyronine (T3) may be considered in patients with persistence of symptoms, despite optimal T4 treatment, based on expert opinion 3, 7.
• The use of liothyronine in primary hypothyroidism is still a matter of debate, and more clinical studies are needed to identify patients who may benefit from this therapy 7.