Rheumatic problems occuring in patients with hyperthyroidism
- Thyroid acropachy
- Painless proximal muscle weakness (70% of hyperthyroidpatients)
- Osteoporosis—most common musculoskeletal manifestation.
- Adhesive capsulitis of the shoulders (controversial), especially in patients with proximal muscle weakness.
Arthropathy associated with severe hypothyroidism
- Myxedematous arthropathy usually affects large joints such as the knees. The patient presents with swelling and stiffness. Synovial thickening, ligamentous laxity, and knee effusions with a characteristic slow fluid wave (bulge sign) are common. The synovial fluid is noninflammatory with an increased viscosity owing to high hyaluronic acid levels giving a string sign of 1 foot to 2 feet instead of the normal 1 inch to 2 inches. Radiographs are typically normal.
- Osteonecrosis can also occur (controversial). In adults, it typically involves the hip or tibial plateau. In children, abnormal epiphyseal ossification may occur, which can be confused with epiphyseal dysplasia or juvenile avascular necrosis (Legg–Calvé–Perthes disease) of the hip.
Other common rheumatologic syndromes associated with hypothyroidism
Think of TRAP:
T—Tunnel (carpal) syndrome (15% of hypothyroid patients).
A—Aching muscles with findings indistinguishable from those of fibromyalgia
(up to 30% of hypothyroid patients).
P—Proximal muscle weakness and stiffness with an elevated creatine kinase. Thyroid-stimulating hormone (TSH) always very high (>20) and thyroxine (T4) low.
Medications used to treat hyperthyroidism that can cause rheumatic syndromes:
- Propylthiouracil—can cause a systemic vasculitis (perinuclear antineutrophil cytoplasmic antibody positive).
- Methimidazole—lupus-like syndrome and a syndrome of diabetes mellitus owing to antiinsulin antibodies.