Systemic lupus erythematosus (SLE), commonly known as lupus, is a chronic autoimmune disease where the immune system mistakenly attacks healthy tissues and organs, such as the skin, joints, kidneys, and heart. The thyroid gland, located in the neck, produces hormones that regulate the body’s metabolism, controlling functions like heart rate and energy levels. There is a strong association between lupus and thyroid problems, with individuals who have SLE being significantly more likely to develop thyroid dysfunction than the general population. This connection is rooted in a shared underlying process of autoimmunity, where the immune system’s aggression can target multiple organs simultaneously.
The Shared Autoimmune Connection
Having one autoimmune disease, such as lupus, substantially increases the risk of developing another, a phenomenon sometimes called polyautoimmunity. This heightened risk is explained by overlapping genetic predispositions that make the immune system prone to self-attack. Specific shared gene variations, particularly those related to the human leukocyte antigen (HLA) complex, increase susceptibility to both SLE and autoimmune thyroid diseases.
The connection also stems from the fundamental immune system dysregulation that occurs in lupus. In SLE, the body produces autoantibodies and experiences hyperactivity of immune cells, such as T-cells and B-cells, which target the body’s own tissues instead of fighting infection. This generalized immune system overactivity can cause the body to recognize the thyroid gland’s proteins as foreign invaders. The resulting inflammation and attack on the thyroid is another manifestation of the same underlying immune system error that causes lupus.
Specific Thyroid Conditions Associated with Lupus
The most frequent thyroid problem seen in people with SLE is autoimmune thyroid disease, which includes Hashimoto’s thyroiditis and Graves’ disease. Hashimoto’s thyroiditis is an autoimmune condition where the immune system attacks and destroys thyroid cells, leading to insufficient hormone production, known as hypothyroidism. Hypothyroidism is the most common thyroid disorder in lupus patients, occurring in an estimated 15% to 19% of the SLE population, which is considerably higher than in the general public.
The symptoms of hypothyroidism include unexplained weight gain, chronic weakness, dry skin, hair loss, and cold intolerance. These symptoms are challenging because they often mimic the non-specific symptoms of a lupus flare, such as fatigue and joint pain. Graves’ disease causes the thyroid to overproduce hormones, resulting in hyperthyroidism. This condition is also more prevalent in SLE patients than in the general population, although it is less common than hypothyroidism.
Hyperthyroidism is characterized by symptoms like a rapid heart rate, unintended weight loss, nervousness, and heat sensitivity. It can be difficult to determine whether these symptoms are due to a new thyroid issue or an increase in lupus disease activity. The coexistence of these two autoimmune conditions requires careful attention, as the symptoms of an over- or under-active thyroid can easily be mistakenly attributed to lupus alone.
Recognizing and Managing Dual Conditions
Given the high rate of co-occurrence, regular screening for thyroid dysfunction is an important part of managing lupus. Blood tests are often recommended to check thyroid function, even if a patient is not experiencing obvious symptoms. Screening involves measuring the levels of Thyroid-Stimulating Hormone (TSH), along with the thyroid hormones free T3 and free T4.
The presence of thyroid antibodies, specifically anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin (anti-Tg) antibodies, can also be checked, as these indicate an ongoing autoimmune attack. If a thyroid problem is identified, treatment is the same as it is for individuals without lupus. For hypothyroidism, the standard treatment is a daily dose of the synthetic hormone levothyroxine to replace the hormones the thyroid gland is no longer making.
For hyperthyroidism, treatment options include anti-thyroid medications, such as methimazole, which reduce hormone production. Because managing a patient with both SLE and thyroid disease is complex, coordinated care between a rheumatologist (who manages lupus) and an endocrinologist (who specializes in the thyroid) is highly beneficial. This multidisciplinary approach ensures that treatment for one condition does not negatively affect the other and that overlapping symptoms are correctly diagnosed.