Endocrinology Flashcards
What is the effect of the parathyroid hormone (PTH) on calcium levels?
Increases plasma Ca2+
What is the effect of calcitonin (CT) on calcium levels?
Decreases plasma Ca2+
What is the effect of vitamin D on calcium levels?
Increases plasma Ca2+
What other hormones have an effect on calcium levels?
Oestrogens
Growth hormone
Glucocorticoids
What are the causes of primary hyperparathyroidism?
Primary hyperparathyoidism
- prevalent
- slowly developing condition
- common endocrine disorder
- 2 - 3 times more common in women than men
Excess parathyroid hormone causes hypercalcaemia and phosphaturia, low plasma phosphate and increased urinary cAMP
Caused by
- single chief cell tumour
- hyperplasia of one or more parathyroid glands
- parathyroid carcinoma
- rare
Can be associated with multiple endocrine neoplasia type 1 involving many endocrine glands
What is the cause of secondary hyperparathyroidism?
Secondary overactivity and hyperplasia of all 4 glands (no hypercalcaemia)
- compensation of hypocalcaemia due to intestinal Ca2+ / vitamin D malabsorption, or deficiency or chronic renal failure
What are the symptoms of hyperparathyroidism?
Bones Stones and Groans!
Tiredness General malaise Depression Weakness Lethargy Dizziness Excessive thirst Anorexia Nausea Vomiting Dehydration Psychiatric disorders Cardiac arrhythmias Heart block GI tract complaints - abdominal pain - constipation - dyspepsia - ulceration Renal stones composed of insoluble calcium phosphate Renal colic and haematuria Renal failure Gallstones Bone lesions following excess resorption of Ca2+ from bone More severe cases - bone cysts - bone pain - fractures
What is the first line treatment for hyperparathyroidism?
Surgical removal of overactive tissue Condition can reoccur - surgery will need to be repeated Can get permanent hypoparathyroidism Risk of damage to laryngeal nerves
Which drugs can be used to treat hyperparathyroidism?
Cinacalet HCl used for refractory secondary hyperparathyroidism in
- end-stage renal disease
- primary hyperparathyroidism if surgery not possible
- parathyroid carcinoma
Monitor serum Ca2+ and PTH concentrations
Paricalcitol in chronic renal failure (vitamin D deficiency)
- synthetic vitamin D analogue
- secondary hyperparathyroidism
What are the side effects of Cinacalet HCl (Mimpara)?
Nausea
Vomiting
Anorexia
Rash
What is hypercalcaemic crisis treated with?
- 9% NaCl infusion and rehydration fluids
- combat dehydration
- increase urinary Ca2+ excretion
Salmon calcitonin and pamidronate disodium used to inhibit bone resorption
What are the causes of hypoparathyroidism?
Damage during thyroid surgery
Rare primary hypoparathyroidism
Autoimmune disease with antibodies against parathyroid tissue
Associated with other endocrine autoimmune conditions
- hypothyroidism
- type I diabetes
- adrenal insufficiency
Can also have psuedohypoparathyroidism
- hereditary
- bone and kidney insensitive to parathyroid hormone
Hypocalcaemia and high plasma phosphate
What are the symptoms of hypoparathyroidism?
Hyperexcitability of nerve and neuromuscular tissues - pins and needles - muscle cramps - muscle spasms - epileptic seizures or convulsions Chvostek's sign - twitching of facial muscles after tapping 7th cranial nerve Trousseau's sign - tetanic spasm of wrist and fingers after over-inflation of a sphygmomanometer cuff for > 3 minutes Dental abnormalities Dry scaly skin and hair Brittle nails Cataracts
What is the treatment for hypoparathyroidism?
Vitamin D supplements
- ergocalciferol
- vitamin D2
- vitamin D derivative
- dihydrotachysterol solution (AT10)
- enhance Ca2+ absorption and utilisation
- IV alfacalcidol
Need to check Ca2+ levels to prevent hypercalcaemia
Acute hypocalcaemic tetany treated with slow IV infusion of 10% calcium gluconate
- parathyroid hormone too expensive to use
What are the therapeutic uses of calcitonin?
Clinical conditions associated with hyposecretion or hypersecretion of calcitonin are very rare
Can get oversecretion with medullary thyroid carcinomas or ectopic tumours
- no imbalance in plasma Ca2+ levels seen
- tumour marker
Removal of thyroid gland does not produce hypercalcaemia
What is Paget’s disease?
Abnormal high rate of bone turnover
- excessive osteoclast bone resorption followed by increased osteoclast activity to repair damage
How common is Paget’s disease?
Common chronic disease affecting ~0.5% of population
> 40 years old
Mainly men
What are the symptoms of Paget’s disease?
Deformation of skull, spine, pelvis and long bones Abnormal bone density Plasma Ca2+ and phosphate normal Can get increased alkaline phosphatase from osteoclasts Joint and bone pain Fractures Bone deformaties - bowed legs Skull enlargement - deafness - squashes aural nerve - blindness - squashes optic nerve
What is the treatment for Paget’s disease?
Bisphophonates
- adsorbed onto hydroxyapatite crystals
- slow rate of formation and dissolution of bone thus reducing resorption
- decrease production of cytokines by osteoblasts thus reduces osteoclast activity
Pamidronate disodium
- IV infusion
Risedronate sodium
- oral
Zoledronic acid
2 - 6 months
May need to monitor serum phosphate and alkaline phosphatase levels and urinary hydroxyproline
What are the side effects of synthetic salmon calcitonin to treat Paget’s disease?
Nausea
Facial flushing
Allergic reactions
Malignancy with long term use
What are hypercalcaemic states associated with?
Malignant disease
- bone metastases
What is used to reduce plasma Ca2+ levels in hypercalcaemic states?
Salcatonin used subcutaneously or intramuscularly to reduce Ca2+ within 24 hours
- also used intravenously in severe cases
What causes resistance to salcatonin?
Receptor downregulation or neutralising antibody function
Give examples of bisphosphonates used to treat hypercalcaemic states
Ibandronic acid
Pamidronate disodium
Sodium clodronate
Zoledronic acid
