Disorders of the Pituitary Gland
Acromegaly presents with arthralgia of the large joints (knees, hips and shoulders), although radiographically changes are noted in the proximal and distal interphalageal joints. Morning stiffness and joint swelling are rare and severity of musculoskeletal complaints seems to correlate with the severity of disease. Patients may also develop proximal muscle weakness, although muscle enzymes are generally normal and biopsy specimens may demonstrate variation in fiber size without inflammation. Fibrous synovial thickening and/or bony overgrowth in the PIP and distal interphalangeal (DIP) joints is reported in 50%. Characteristic radiographic changes include an enlarged sella turcica, increased thickness and enlargement of the frontal sinuses, elongation of the mandible, soft tissue thickening, broad metacarpals and phalanges, prominent distal tufts, widened joint spaces (due to cartilage hypertrophy), increased thickness of the heel pad, broadening of the sternal ends of the ribs, kyphosis and enlargement of the vertebral bodies. Growth hormone (increased in acromegaly) secreted by the anterior pituitary acts on hepatocytes to secrete somatomedins which have stimulatory effects on bone and cartilage (chondrocyte replication, synthesis of proteogylcans, collagen, osteoblastic proliferation, and increased bone collagen) resulting in increased bone mass. Sometomedins also have insulin-like activity on muscle and fat. Treatment is aimed at decreasing the size of the adenoma (surgically, ultrasound or laser) and success may not result in changes in the musculoskeletal findings or symptoms.