Autoimmune Polyendocrine Syndrome Type 3 (APS3)

Autoimmune Polyendocrine Syndrome Type 3 (APS3) is an autoimmune condition where the immune system attacks multiple hormone-producing glands, most notably the thyroid. It always includes autoimmune thyroid disease, such as Hashimoto's thyroiditis or Graves' disease, and at least one other autoimmune disease - but never involves the adrenal glands (unlike APS1 and APS2).

Fatigue; Weight changes; Cold or heat intolerance; Constipation or diarrhea; Mood swings or anxiety; Hair thinning or loss; Irregular menstrual cycles. Specific conditions seen in APS3 include Hashimoto's thyroiditis, Graves' disease, Type 1 diabetes (LADA), Celiac disease, and Pernicious anemia.

Genetic predisposition (HLA genes, especially HLA-DR3, DR4, and DQ2/DQ8; CTLA4 gene; PTPN22 gene); Immune system dysregulation leading to loss of immune tolerance; Environmental triggers (viral infections, stress, gut dysbiosis, vitamin D deficiency, gluten exposure).

Diagnosis is clinical based on presence of autoimmune thyroid disease and at least one other autoimmune disorder, but no adrenal insufficiency. Tests: Thyroid antibody panels (anti-TPO, anti-thyroglobulin); Blood sugar and HbA1c; Vitamin B12 levels and anti-intrinsic factor antibodies; Tissue transglutaminase antibodies (for celiac disease).

No cure; each component disease is treated individually: Thyroid hormone replacement (levothyroxine for Hashimoto's); Anti-thyroid drugs or radioactive iodine (for Graves'); Insulin (if diabetes is present); Gluten-free diet (for celiac disease); Vitamin B12 injections (for pernicious anemia). Patients need lifelong follow-up.

Prognosis is generally good with proper treatment. However, patients may develop additional autoimmune conditions over time, so regular monitoring is essential.

Exact prevalence unknown but more common than APS1 and APS2 due to the high rate of autoimmune thyroid disease. More frequent in middle-aged women and those with a family history of autoimmunity.