Subclinical Hypothyroidism and Disease Activity in Rheumatoid Arthritis

Prevalence of Subclinical Hypothyroidism in Patients of Rheumatoid Arthritis and Its Relation to Disease Activity

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disorder that causes persistent joint inflammation and damage. Thyroid disorders, particularly subclinical hypothyroidism, are common co-existing conditions in patients with autoimmune diseases. Subclinical hypothyroidism occurs when the thyroid gland is mildly underactive, characterized by an elevated thyroid-stimulating hormone (TSH) level with normal free thyroxine (FT4) levels.

The primary purpose of this cross-sectional study is to determine how common subclinical hypothyroidism is among Egyptian patients with rheumatoid arthritis compared to an age- and sex-matched group of healthy individuals. Additionally, the study aims to evaluate whether the presence of subclinical hypothyroidism is linked to higher rheumatoid arthritis disease activity, severe joint involvement, or specific clinical characteristics.

A total of 150 adult participants will be included: 75 patients diagnosed with rheumatoid arthritis and 75 healthy controls. All participants will undergo a clinical evaluation, joint examinations, and standard blood tests, including complete blood counts, inflammatory markers, and a thyroid hormone panel (TSH, FT4, and FT3). Disease activity in rheumatoid arthritis patients will be evaluated using the Disease Activity Score-28 (DAS28).

Inclusion Criteria:

• Age ≥ 18 years, either sex
• Diagnosis of rheumatoid arthritis according to the 2010 ACR/EULAR classification criteria (for the case group)
• Apparently healthy individuals with no history of joint disease or known thyroid disorder, matched for age and sex (for the control group)
• Willingness to provide written informed consent

Exclusion Criteria:

• Known pre-existing thyroid disease diagnosed prior to rheumatoid arthritis onset
• Current or recent (within 6 months) use of medications known to affect thyroid function (e.g., amiodarone, lithium, interferon)
• Pregnancy or lactation
• Other systemic autoimmune diseases that could independently affect thyroid function (e.g., systemic lupus erythematosus, overlap syndromes)
• History of thyroid surgery or radioactive iodine therapy
• Chronic kidney or liver disease
• Ongoing severe infections
• Malignancy