Hyperparathyroidism

Hyperparathyroidism is the effect of excess parathyroid hormone in the body. It can be primary, secondary, or tertiary. There are many characteristic imaging features, predominantly involving the skeletal system.

It accounts for the 'H' in the popular mnemonic for lucent bone lesions FEGNOMASHIC.

Clinical presentation

Parathyroid hormone affects multiple organs. The most common symptoms are bone pain, chronic fatigue, polyuria, headache, decreased concentration and depression. Also, patients can present with complications like renal stones, fractures, cardiac arrhythmia, and hypertension.

Hyperparathyroidism is supported biochemically by either an elevated serum parathyroid hormone level or an inappropriately normal level in the setting of hypercalcemia.

Epidemiology

Associations

Hyperparathyroidism can occur in the context of the following conditions from parathyroid hyperplasia or less commonly multiple parathyroid adenomas ⁵:

• multiple endocrine neoplasia type I (MEN1)

• multiple endocrine neoplasia type IIa (MEN2a)

• familial hypocalciuric hypercalcemia

• familial isolated primary hyperparathyroidism

• hyperparathyroidism-jaw tumor syndrome

Pathology

Increased levels of the parathyroid hormone lead to increased osteoclastic activity. The resultant bone resorption produces cortical thinning (subperiosteal resorption) and osteopenia.

Subtypes

• primary hyperparathyroidism

  • parathyroid adenoma (~80%)

    • multiple parathyroid adenomas (4%) ⁵

  • parathyroid hyperplasia (10-15%) ^2,5

  • parathyroid carcinoma (1-5%) ^4,5

  • parathyromatosis (very rare)

• secondary hyperparathyroidism

  • caused by chronic hypocalcemia with renal osteodystrophy being the most common cause (others include malnutrition, vitamin D deficiency) ⁴

  • results in parathyroid hyperplasia ⁷

• tertiary hyperparathyroidism

  • autonomous parathyroid adenoma caused by the chronic overstimulation of hyperplastic glands in renal insufficiency

Radiographic features

• subperiosteal bone resorption

  • classically affects the radial aspects of the proximal and middle phalanges of the 2^nd and 3^rd fingers

  • medial aspect of tibia, femur, humerus

  • lamina dura: floating teeth (not specific)

• subchondral resorption

  • lateral end of the clavicles

  • symphysis pubis

  • sacroiliac joints

• subligamentous resorption

  • ischial tuberosity

  • trochanters

  • inferior surface of calcaneus and clavicle

• intracortical resorption: cigar/oval-shaped or tunnel-shaped radiolucency in the cortex

• terminal tuft erosion (acro-osteolysis)

• rugger jersey spine

• osteopenia

• brown tumors

• salt and pepper sign in the skull (pepper pot skull)

• chondrocalcinosis

Findings in secondary (and tertiary) hyperparathyroidism are often associated with the osteosclerosis of renal osteodystrophy and the osteomalacia of vitamin D deficiency:

• subperiosteal bone resorption

• osteopenia

• osteosclerosis, e.g. rugger jersey spine

• soft tissue calcification

• superscan: generalized increased uptake on Tc-99m pertechnetate bone scan (focal uptake with adenoma)

• superior and inferior rib notching