Calcium homeostasis disorders

Question 1

What are the causes of primary hypersecretion of parathyroid hormone?

Answer 1

Caused by single chief cell tumour, hyperplasia, or carcinoma (multiple endocrine neoplasia type 1)
Prevalent, slow developing, more common in females
Excess PTH- hypercalcaemia and phosphaturia, low plasma phosphate, increased urinary cAMP

Question 2

What are the causes of secondary hypersecretion of parathyroid hormone?

Answer 2

Overactivity and hyperplasia of all four glands

Compensation for hypocalcaemia due to intestinal calcium/ vitamin D absorption or deficiency/ chronic heart failure

Question 3

What are the symptoms of hypersecretion of parathyroid hormone?

Answer 3

Tiredness depression, nausea and vomiting, anorexia, thirsty, cardiac arrhythmias
Abdominal pain, constipation, dyspepsia, ulcers
Renal stones, renal colic and haematuria, renal failure
Bone lesions due to excess calcium resorption from bone

Question 4

What is the treatment for parathyroid hypersecretion?

Answer 4

Surgical removal of overactive tissue
Cinacalcet HCl- used for refractory secondary hyperparathyroidism in end stage renal disease, primary hyperparathyroidism and parathyroid carcinoma- monitor serum calcium and PTH concs
Paracalcitol- secondary hyperparathyroidism in chronic renal failure
0.9% NaCl infusion- to treat hypercalcaemic crisis with rehydration fluids to rehydrate and increase urinary calcium excretion
Salmon calcitonin and disodium pamidronate to inhibit bone resorption

Question 5

What are the causes of hyposecretion of parathyroid hormone?

Answer 5

Damage during thyroid surgery
Rare primary hyposecretion- autoimmune disease with antibodies against parathyroid tissue, associated with hypothyroidism, type 1 diabetes and adrenal insufficiency
Can also have pseudohyposecretion, hereditary, bone and kidney insensitive to PTH
Hypocalcaemia and high plasma phosphatase

Question 6

What are the symptoms of hyposecretion of parathyroid hormone?

Answer 6

Hyperexcitability of nerve and neuromuscular tissue, muscle spasms, muscle cramps and seizures
Chvostek’s sign- facial muscle twitching after tapping seventh cranial nerve
Trousseas’s sign- tetanic wrist and finger spasms after overinflation of BP cuff for > 3 minutes
Dental abnormalities, dry scaly skin and hair, brittle nails

Question 7

What is the treatment for hyposecretion of parathyroid hormone?

Answer 7

Vitamin D supplements/ Vitamin D derivative/ dihydrotachysterol solution to enhance calcium absorption and utilisation
Need to check calcium levels to prevent hypercalcaemia
Slow IV infusion of 10% calcium gluconate- acute hypocalcaemic tetany

Question 8

What are the uses of calcitonin?

What causes oversecretion?

Answer 8

Conditions associated with hypo/hypersecretion

Can get oversecretion with medullary thyroid carcinomas/ectopic tumours

Question 9

What are the causes of Paget’s disease?

Answer 9

Mainly men
Abnormal high rate of bone turnover, excessive osteoclast bone resorption followed by increased osteoblasts to repair damage

Question 10

What are the symptoms of Paget’s disease?

Answer 10

Deformation of skull, spine, pelvis and long bones
Plasma calcium and phosphate normal
Joint and bone pain, fractures, bone deformities, skull enlargement

Question 11

What is the treatment of Paget’s disease?

Answer 11

Bisphosphonates absorbed onto hydroxyapatite crystals- slows formation and dissolution of bone, decreases production of cytokines by osteoblasts to reduce osteoclastactivity
Pamidronate disodium IV, risedronate sodium, zoledronic acid IV for 2-6 months, many side effects
Synthetic salmon calcitonin SC/IM- max 3 months, long term use can cause malignancy
Monitor serum phosphate and alkaline phosphatase levels and urinary hydroxyproline

Question 12

Hypercalcaemic states

Answer 12

Associated with malignant disease (bone metastases)
Salcatonin SC/IM- reduce plasma calcium in 24 hours
Can get resistance due to receptor downregulation or neutralising antibody formation
Use ibandronic acid, pamidronate disodium, sodium carbonate and zoledronic acid

Question 13

Clinical disorders of calcitriol- adults and children

Answer 13

Vitamin D deficiency- rickets in children, osteomalacia in adults

Question 14

What are the causes of vitamin D deficiency?

Answer 14

Metabolic abnormality- inherited absence/ reduced activity of 1a-hydroxylase
Vit D dependent rickets types 2- defect in VDR gene
Intestinal fatmalabsorption
Chronic liver disease
Lack of sunlight
Dietary lack

Question 15

What are the symptoms of vitamin D deficiency in adults and children?

Answer 15

Children- swollen growing bone ends, bowed legs
Adults- bone pain, partial fractures and muscle weakness
Inadequate calcification of matrix and softening of skeleton
VDDR2- high plasma calcitriol levels and severe alopecia

Question 16

What is the treatment for vitamin D deficiency?

Answer 16

Small oral doses and sometimes a calcium supplement- dietary prevention/ insufficiency
Higher doses for deficiency in children, also with anticonvulsants e.g. calcichew D3,
Ergocalciferol does to 1mg- intestinal malabsorption/ hepatic disease
Alfacalcidol- severe renal impairment and VDDR1
High dose of vitamin D/active metabolites- VDDR2
Plasma and urinary calcium monitored- check for hypercalcaemia and vitamin D toxicity
Not for breast feeding- high doses of vitamin D supplements

Question 17

What are the causes of vitamin D excess?

Answer 17

Overuse of vitamin D supplements (>10,000 IU daily) for over 12 weeks
Sarcoidosis- chronic, benign, systemic, nodules of inflamed tissue in skin and other organs composed of epithelial, monocytes and macrophages
Skin condition associated with enhanced vit D3 synthesis after sun exposure or excess ingestion

Question 18

What are the symptoms and treatment of vitamin D excess?

Answer 18

Symptoms- hypercalcaemia- tiredness, anorexia, nausea and vomiting
Treatment- reduce dose of vitamin D preparation
Systemic/local corticosteroids- sarcoidosis