Can a patient have both Hashimoto's thyroiditis (HT) and hypothyroidism?

From the Guidelines

Yes, a patient can have both Hashimoto's thyroiditis (HT) and hypothyroidism, as Hashimoto's is the most common cause of hypothyroidism in the United States. Hashimoto's is an autoimmune condition where the immune system attacks the thyroid gland, gradually damaging it and reducing its ability to produce thyroid hormones, which eventually leads to hypothyroidism, the underactive state of the thyroid 1. The connection between these conditions is straightforward: Hashimoto's is the process (the autoimmune attack), while hypothyroidism is the result (decreased thyroid function).

Key Points to Consider

• Hashimoto's thyroiditis is the most common cause of hypothyroidism, with risk factors including female sex, advancing age, white race, type 1 diabetes, Down syndrome, family history of thyroid disease, goiter, previous hyperthyroidism, and external-beam radiation in the head and neck area 1.
• The serum TSH test is the primary screening test for thyroid dysfunction, with multiple tests done over a 3- to 6-month interval to confirm or rule out abnormal findings 1.
• Treatment for hypothyroidism typically involves oral T4 monotherapy (levothyroxine sodium), with the goal of normalizing TSH levels 1.

Treatment and Management

• Treatment typically involves daily thyroid hormone replacement with levothyroxine, usually starting at doses of 1.6 mcg per kg of body weight, though older adults may start at lower doses (25-50 mcg daily) 1.
• The doctor will monitor TSH levels every 6-8 weeks initially and adjust the medication dose until levels normalize, with annual testing thereafter.
• Many people with Hashimoto's will eventually develop hypothyroidism as their thyroid gland becomes more damaged over time, though the progression rate varies significantly between individuals 1.

From the Research

Hashimoto's Thyroiditis and Hypothyroidism

• Hashimoto's thyroiditis is a common cause of hypothyroidism, and patients with this condition often require lifelong thyroid replacement therapy 2.
• Studies have shown that hypothyroidism caused by Hashimoto's thyroiditis is not always permanent, and some patients may experience remission 2.
• The presence of a larger goiter, high thyrotropin levels, and a familial incidence of thyroid disease may be associated with an increased incidence of hypothyroidism remission 2.

Coexistence of Hashimoto's Thyroiditis and Hypothyroidism

• Hashimoto's thyroiditis and hypothyroidism can coexist, and patients may experience transitions between hypothyroidism and hyperthyroidism 3, 4.
• The coexistence of Hashimoto's thyroiditis and Graves' disease can lead to transitions between hypothyroidism and hyperthyroidism, influenced by the predominance of involved antibodies and residual capacity of thyroid tissue 3.
• Patients with Hashimoto's thyroiditis may develop hypothyroidism, and in some cases, may convert to hyperthyroidism 4.

Diagnosis and Treatment

• Diagnosis of Hashimoto's thyroiditis and hypothyroidism requires a detailed medical history, sonography, and blood analysis of thyroid function and thyroid antibodies 5.
• Treatment of hypothyroidism caused by Hashimoto's thyroiditis typically involves long-term or lifelong levothyroxine replacement therapy 2, 5.
• Patients with Hashimoto's thyroiditis and hypothyroidism may require careful monitoring and adjustment of their treatment regimen to prevent over-replacement or under-replacement of thyroid hormone 4.