Hyperparathyroidism Flashcards
Which cells produce PTH
Chief cells in the glands, produce parathyroid hormone in response to hypocalcaemia (low blood calcium).
How does PTH raise blood calcium
Increasing osteoclast activity in bones (reabsorbing calcium from bones)
Increasing calcium absorption from the gut
Increasing calcium absorption from the kidneys
Increasing vitamin D activity
How does vitamin D increase blood calcium levels
Acts to increase calcium absorption from the intestines.
Parathyroid hormone acts on vitamin D to convert it into active forms. So vitamin D and parathyroid hormone act together to raise blood calcium levels.
Symptoms of hypercalcaemia
Renal stones
Painful bones
Abdominal groans refers to symptoms of constipation, nausea and vomiting
Psychiatric moans refers to symptoms of fatigue, depression and psychosis
What is primary hyperparathyroidism caused by
Uncontrolled parathyroid hormone produced directly by a tumour of the parathyroid glands.
This leads to hypercalcaemia
How is primary hyperparathyroidism treated
Surgical removal of tumour
What is secondary hyperparathyroidism
Where insufficient vitamin D or chronic renal failure leads to low absorption of calcium from the intestines, kidneys and bones.
This causes hypocalcaemia
Why is there raised PTH in secondary hyperparathyroidism
The parathyroid glands reacts to the low serum calcium by excreting more parathyroid hormone.
Over time the total number of cells in the parathyroid glands increase as they respond to the increased need to produce parathyroid hormone.
This is called hyperplasia. The glands become more bulky. The serum calcium level will be low or normal but the parathyroid hormone will be high.
How is secondary parathyroidism treated
Correcting the vitamin D deficiency or performing a renal transplant to treat renal failure.
What causes tertiary hyperparathyroidism
This happens when secondary hyperparathyroidism continues for a long period of time.
It leads to hyperplasia of the glands. The baseline level of parathyroid hormone increases dramatically.
Then when the cause of the secondary hyperparathyroidism is treated the parathyroid hormone level remains inappropriately high.
This high level of parathyroid hormone in the absence of the previous pathology leads to high absorption of calcium in the intestines, kidneys and bones and causes hypercalcaemia.
How is tertiary hyperparathyroidism treated
Surgically removing part of the parathyroid tissue to return the parathyroid hormone to an appropriate level.
Pathophys of paget’s disease of bone
There is excessive bone turnover due to excessive activity of both osteoblasts and osteoclasts leading to sclerosis and lysis
Presentation of paget’s disease
Bone pain
Bone deformity
Fractures
Hearing loss can occur if it affects the bones of the ear
X-ray findings in paget’s disease of the bone
Bone enlargement and deformity
Osteoporosis circumscripta
Cotton wool appearance of skull
V-shaped defects
What is osteoporosis circumscripta
Describes well defined osteolytic lesions that appear less dense compared with normal bone
What does cotton wool appearance of skull in paget’s disease refer to
describes poorly defined patchy areas of increased density (sclerosis) and decreased density (lysis)
What are V-shaped defects in Paget’s disease of the bone
“V-shaped defects” in the long bones are V shaped osteolytic bone lesions within the healthy bone
Biochem findings in Paget’s disease of the bone
Raised alkaline phosphatase (and other LFTs are normal)
Normal calcium
Normal phosphate
Predisposing factors for Paget’s disease of the bone
increasing age
male sex
northern latitude
family history
Management of Paget’s disease of the bone
Bisphosphonates
NSAIDs for bone pain
Calcium and vitamin D supplements
Surgery rarely
Complications of Paget’s disease of the bone
deafness (cranial nerve entrapment) osteosarcoma fractures skull thickening high-output cardiac failure Spinal stenosis
Initial management of hypercalcaemia
IV fluid therapy(3-4l/day)
Following rehydration bisphosphonates may be used
Other options for management of hypercalcaemia
calcitonin - quicker effect than bisphosphonates
steroids in sarcoidosis
What is osteomalacia
Osteomalacia is a condition where there is defective bone mineralisation causing “soft” bones
This results from insufficient vitamin D
What are looser zones
Fragility fractures that go partially through the bone
Risk factors for osteomalacia
Darker skin
Low exposure to sunlight
Colder climates
Time indoors
Interpretation of serum 25-hydroxyvitamin D levels
<25 nmol/L – vitamin D deficiency
25 – 50 nmol/L – vitamin D insufficiency
75 nmol/L or above is optimal
Treatment of osteomalacia
Treatment is with supplementary vitamin D
