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Graves disease is the most common cause of hyperthyroidism in young women. It is mediated by TSH receptor–stimulating antibodies (thyroid-stimulating immunoglobulin), which mimic TSH and cause unregulated thyroid hormone production. Clinical features include weight loss, palpitations, tremor, ophthalmopathy (exophthalmos), and pretibial myxedema. Anti-thyroid peroxidase and anti-thyroglobulin antibodies are markers of Hashimoto thyroiditis. TSH receptor blocking antibodies are associated with hypothyroidism, not hyperthyroidism. Diagnosis is confirmed with suppressed TSH, elevated T4, and positive TSI. Management includes antithyroid drugs (methimazole, PTU), radioactive iodine ablation, or thyroidectomy. Beta-blockers are used for symptomatic relief.

This is medullary thyroid carcinoma (MTC), a neuroendocrine tumor of parafollicular C cells. It secretes calcitonin, which can deposit as amyloid in the tumor stroma, producing apple-green birefringence under polarized light after Congo red staining. MTC is associated with germline RET proto-oncogene mutations (MEN2A and MEN2B). Thyroglobulin is secreted by differentiated thyroid cancers such as papillary and follicular carcinoma, not MTC. PTH comes from parathyroid glands; cortisol is secreted by the adrenal cortex. Calcitonin levels can be used as a tumor marker for diagnosis and recurrence monitoring. Management requires total thyroidectomy, with prophylactic surgery recommended in MEN2 mutation carriers. Unlike papillary carcinoma, MTC does not take up radioactive iodine, making radioiodine therapy ineffective.

Pancreatic adenocarcinoma commonly arises in the head of the pancreas and presents with painless jaundice (biliary obstruction), weight loss, and a palpable, nontender gallbladder or epigastric mass (Courvoisier sign). Risk factors include chronic alcohol use, chronic pancreatitis, smoking, diabetes, and family history. Elevated bilirubin and alkaline phosphatase suggest cholestasis due to obstruction of the common bile duct. Gastric carcinoma typically presents with epigastric discomfort, anemia, or weight loss but not obstructive jaundice. Hepatocellular carcinoma arises in the setting of cirrhosis or hepatitis B/C, presenting with liver mass and elevated alpha-fetoprotein. Cholangiocarcinoma is a bile duct malignancy associated with primary sclerosing cholangitis, often presenting with jaundice but less likely to cause a firm pancreatic head mass. Diagnosis of pancreatic cancer often involves CT or MRI of abdomen, CA 19-9 marker, and biopsy confirmation. Prognosis is poor; surgical resection (Whipple procedure) is the only curative option in localized disease, but many present late. Palliative care may include stenting for biliary obstruction and systemic chemotherapy.

Osteoarthritis is a degenerative joint disease characterized by cartilage loss, subchondral bone changes, and osteophyte formation. It presents with pain that worsens with activity and improves with rest. Commonly affected joints include the DIP, PIP, knees, and hips. Morning stiffness is brief (<30 minutes), unlike rheumatoid arthritis, which has prolonged stiffness. X-ray shows joint space narrowing, subchondral sclerosis, and osteophytes. RA presents with symmetric joint involvement, systemic inflammation, and positive rheumatoid factor/anti-CCP antibodies. Gout presents with acute monoarthritis and negatively birefringent urate crystals. Psoriatic arthritis involves DIP joints with nail pitting and dactylitis. Osteoarthritis management includes weight loss, NSAIDs, intra-articular injections, and joint replacement in severe cases.

Osteosarcoma is the most common primary malignant bone tumor in adolescents. It typically arises in the metaphysis of long bones, especially the distal femur or proximal tibia, presenting with pain, swelling, and decreased range of motion. Radiographs show a destructive lesion with periosteal reaction producing a “sunburst” pattern and lifting of the periosteum (Codman triangle). Ewing sarcoma occurs in the diaphysis, with “onion-skin” periosteal reaction. Osteoid osteoma is a benign lesion causing nocturnal pain relieved by NSAIDs. Giant cell tumor occurs in the epiphysis, often around the knee, and appears as a lytic “soap-bubble” lesion. Osteosarcoma management includes chemotherapy and limb-sparing surgery. Early diagnosis is key for survival.