Hyperparathyroidism

Question 1

Imaging features of primary hyperPTH?

(excess PTH leads to excessive osteoclastic activity)

Answer 1

1) SUBPERIOSTEAL bone resorption
- Acro-osteolysis
- classically affects the radial aspects of the proximal and middle phalanges of the 2nd and 3rd fingers
- medial aspect of tibia, femur, humerus
- lamina dura of mandible: floating teeth (not specific)

2) SUBCHONDRAL bone resorption:
- lateral end of the clavicles
- symphysis pubis
- sacroiliac joints

3) SUBLIGAMENTOUS resorption
- ischial tuberosity
- trochanters
- inferior surface of calcaneus and clavicle

4) Brown tumors. Expansile well-defined geographic lytic lesions with narrow zone of transition. (mandible, hands, pelvis, ribs)

5. Osteopenia
6. Osteosclerosis (diffusely coarsened trabeculae, rugger jersey spine, salt and pepper skull; UNLIKE pagets which is usu not so uniform)

Question 2

What are the 3 types of hyperparathyroidism

Answer 2

1. Primary
   - due to hyperfunctioning parathyroid adenoma (80%) > gland hyperplasia (10-15%) > carcinoma (5%) [can be confirmed on Technetium nuclear scintigraphy (TS) with sestamibi/tetrosfosmin]
2. Secondary
   - caused by chronic hypocalcaemia with renal osteodystrophy being the most common cause (others include malnutrition, vitamin D deficiency)
   - results in parathyroid hyperplasia
3. Tertiary
   - autonomous parathyroid adenoma caused by the chronic overstimulation of hyperplastic glands in renal insufficiency

Question 3

Imaging findings of secondary (or tertiary) hyper PTH?

Answer 3

The 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/chondrocalcinosis
• superscan: generalised increased uptake on Tc-99m pertechnetate bone scan (cf

superior and inferior rib notching