Parathyroid Hormone and Calcium Homeostasis

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What does a family history of hypercalcaemia raise the possibility of?

Familial hypocalciuric hypercalcemia

What do high plasma phosphate and alkaline phosphatase levels accompanied by renal impairment suggest?

Tertiary hyperparathyroidism

What can hypercalcaemia cause that may result in hyperuricaemia and hyperchloraemia?

Nephrocalcinosis

What is the net effect of prolonged exposure of bone to high levels of PTH?

Mobilisation of calcium into the extracellular fluid

What is the effect of pulsatile release of PTH on bone?

Causes net bone gain

What is the most common cause of hypercalcaemia?

Malignancy

What are the classic symptoms associated with primary hyperparathyroidism?

Bones, stones and abdominal groans

What is the role of parathyroid hormone (PTH) in regulating calcium and phosphate homeostasis?

Enhancing calcium absorption from the gut by promoting the conversion of 25-hydroxyvitamin D to the active metabolite

How do the parathyroid chief cells respond to changes in calcium concentrations?

By directly interacting with the calcium-sensing receptor located on the cell surface

What happens to PTH secretion when serum ionized calcium levels fall?

It rises

What is the main function of PTH on the skeleton?

Increasing osteoclastic bone resorption and bone formation

What is the most likely diagnosis if PTH levels are detectable or elevated in the presence of hypercalcaemia?

Primary hyperparathyroidism

What does a biochemical presentation similar to primary hyperparathyroidism with low urinary calcium excretion indicate?

Familial hypocalciuric hypercalcemia

What condition is suggested by high plasma phosphate and alkaline phosphatase levels accompanied by renal impairment?

Tertiary hyperparathyroidism

What is the recommended initial medical management for severe hypercalcaemia?

IV 0.9% saline 2–4 L/day

What is the duration of action of calcitonin in the treatment of hypercalcaemia?

4 weeks

In the medical management of severe hypercalcaemia, what is the alternative option for patients with refractory hypercalcaemia if zoledronic acid is not effective?

Denosumab initial dose 60 mg SC

What is the most common cause of hypocalcaemia?

Low serum albumin with normal ionised calcium concentration

How does magnesium depletion cause hypocalcaemia?

By impairing the ability of parathyroid glands to secrete PTH

What is the effect of hypomagnesaemia on serum phosphate levels?

Causes variable serum phosphate levels

How should calcium be adjusted in the presence of hypoalbuminaemia?

Increase by 0.02 mmol/L for every 1 g/L reduction in albumin below 40 g/L

What is the characteristic phenotype associated with pseudohypoparathyroidism?

High serum phosphate and alkaline phosphatase levels accompanied by renal impairment

What is the characteristic triad of symptoms seen in children with tetany?

Carpopedal spasm, stridor, and convulsions

What is the latent tetany detected by eliciting Trousseau’s sign?

Inflation of a sphygmomanometer cuff on the upper arm followed by carpal spasm within 3 minutes

What may prolonged hypocalcaemia and hyperphosphataemia cause in association with hypoparathyroidism?

Calcification of the basal ganglia, grand mal epilepsy, and psychosis

What is the recommended initial management for severe hypocalcaemia?

$10–20 mL 10% calcium gluconate IV over 10–20 mins

What may hypocalcaemia associated with hypophosphataemia cause in children and adults?

Rickets in children and osteomalacia in adults

Explore the role of parathyroid hormone (PTH) in regulating calcium and phosphate levels, as well as its impact on vitamin D metabolism. Learn about the consequences of altered PTH function in gut and renal disease, metabolic bone diseases, disorders of the parathyroid glands, hypercalcemia, and hypocalcemia.

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