Parathyroid disorders
i) Hyperparathyroidism: It is a disorder characterized by increased PTH secretion from the parathyroid glands.
Types of hyperparathyroidism
| Type | Characteristics |
| Primary | Increased PTH secretion by the parathyroid gland, adenoma or parathyroid hypertrophy, lithium adverse effect; most common in postmenopausal women; familial cases present in younger ages; seen in MEN I and II |
| Secondary | Rise to PTH secondary to any cause of hypocalcemia such as Vit D deficiency, low calcium intake, malabsorption, chronic renal failure |
| Tertiary | Due to prolonged hypocalcemia especially in chronic renal failure resulting in autonomous and/or hypertrophied parathyroid gland that secretes excess PTH; persistence of secondary hyperparathyroidism even after renal transplant; change in set point of calcium sensing mechanisms |
Most cases of hyperparathyroidism are asymptomatic. Clinical features are mainly from hypercalcemia or underlying condition such as renal failure and include constipation, bone pains, renal stones, abdominal pain, polyuria, pancreatitis, peptic ulcers, fractures, diastolic hypertension, chondrocalcinosis, psychosis, confusion and anxiety. Some cases may show valvular calcifications, left ventricular hypertrophy and depression. Osteitis fibrosa cystica is a bone disorder seen in hyperparathyroidism and is characterized by bone pain, subperiosteal bone resorption, osteolysis, “salt and pepper” appearance of the skull, bone cysts and “brown tumors” of the bones. Brown tumors are not neoplasms but they are hemorrhagic areas with reparative granulation tissue that looks brown from hemosiderin. Bone lesions are due to increased osteolytic activity caused by stimulation of osteoclasts by excess PTH. Serum alkaline phosphatase levels will be elevated. Hypercalcemia may rarely cause calciphylaxis which presents with skin necrosis, purple discoloration of skin, ulceration and crusting of the skin especially in areas with high fat content like abdomen and inner thigh. It is seen in secondary hyperparathyroidism due to activation of clotting factors and thrombosis of small blood vessels with resulting ischemic skin necrosis.
Laboratory findings in hyperparathyroidism
Condition: Primary hyperparathyroidism
- PTH: High
- Serum calcium: High
- Serum phosphate: Low
Condition: Secondary hyperparathyroidism
- PTH: High
- Serum calcium: Low or low - normal
- Serum phosphate: High in renal failure; Low in Vit D deficiency
Condition: Tertiary hyperparathyroidism
- PTH: High
- Serum calcium: High or normal
- Serum phosphate: High
All symptomatic and severe cases of primary hyperparathyroidism are treated by parathyroidectomy. Technetium 99m sestamibi scan with or without PET scan is a highly sensitive and specific test for the localization of abnormal parathyroid glands. After parathyroidectomy, patients with large adenomas may develop “hungry bone syndrome,” which is associated with hypocalcemia, hypophosphatemia, and low urinary calcium excretion. Secondary and tertiary hyperparathyroidism are managed with calcium and Vit D supplementation. Severe bone disease is treated by parathyroidectomy. Hypercalcemia is treated with intravenous saline, loop diuretics like furosemide, calcitonin and bisphosphonates. Cinacalcet sensitizes the calcium sensing receptor and decreases PTH levels.