Endocrine Flashcards
Definition of hypernatremia
- Electrolyte imbalance consisting of a rise in serum sodium conc.
- More than 145 mmol/L
- Severe = 150 - 160 mmol/L
- Represents a water deficit relative to sodium and can result from a number of causes.
- Mainly occurs in hospitals in ITU.
Aetiology of hypernatremia
- Insufficient fluid intake in elderly, neonates or unconscious patients due to lack of access to water/confusion/coma.
- Exacerbated by increased fluid loss - diarrhoea/sweating.
- Associated with diabetes insipidus.
Presentation of hypernatremia
- Non specific: nausea, vomiting, fever and confusion.
- Usually those in hospital or elderly in nursing homes.
Investigations of hypernatremia
- Simultaneous urine and plasma osmolality and serum sodium.
- If urine osmolality is less than that of blood this is abnormal = Diabetes insipidus.
- If urine osmolality is more than that of blood this suggests osmotic diuresis or extrarenal water loss (Heat stroke)
Management of hypernatremia
- Underlying cause and replace water (Oral or IV with 5% dextrose).
- Aim to treat over 48 hrs due to increased fluid intake can lead to cerebral oedema.
- Severe hypernatremia should also be treated using NaCl 0.9% as there could be a significant drop in sodium.
Complications of hypernatremia
- Treatment related brain oedema/ hyperglycaemia
- Metabolic complications
Definition of hyponatremia
- Low sodium plasma volume
- Defined when plasma volume is less than 135 mmol/L
- A disease of water balance - too much total body water in comparison to electrolytes leading to low plasma osmolarity.
Aetiology and risk factors of hyponatremia
- Elderly, hospitalisations, patients taking SSRIs and thiazide like diuretics.
- Causes depends on the hypovalaemia, normovalaemia and hypervolemia.
Pathophysiology of hyponatremia
- If there is an excess of water in hyponatremia, this could be due to an increase in renal water uptake due to increased levels of vasopressin.
- If there is excess salt loss along with water, this can be due to diseases such as real conditions and diarrhoea.
Presentation of hyponatremia
- Salt loss: Thirst, nausea and postural dizziness due to hypovolaemia and extra cellular depletion.
- Water excess: Doesn’t usually present until sodium levels less than 120 mmol/L but can lead to headache, vomiting, nausea and irritability. In severe cases, the patient may present in a common.
Investigations of hyponatremia
- Find the cause.
Management of hyponatremia
- Treat the underlying cause.
- If salt loss is the reason for the hyponatremia: Replace the extra cellular volume depletion, collaids/crystalloids and also ORT.
- If water excess: controlled fluid restriction, possible use of vasopressin 2 receptor antagonists and also diuretics.
How are calcium levels controlled within the blood?
- Calcium is controlled by PTH and vitamin D acting on the GI tract, kidney and the bone.
- Increased levels of PTH, lead to increase calcium in the serum.
- This is due to increased calcium reabsorption in the kidneys and also the conversion of vitamin D into it’s most active form, which then stimulates the GI tract to absorb calcium and phosphate.
- In the kidney, 1A - hydroxylase converts calidriol into calcitriol, which also stimulates bone resorption and the release of calcium from the bone. This is also stimulated by the calcium intself. The conversion also increase absorption in the gut.
Definition of hypercalcaemia
- Increased calcium levels in the blood.
- Most commonly seen in elderly women.
Aetiology of hypercalcaemia
- Primary hyperparathyroidism and malignancy.
- Malignancy can release a peptide like derivative of PTH or directly invade the bone causing the mobilisation of calcium.
What is normal calcium homeostasis?
- Increased calcium leads to increased calcitonin acting on the thyroid gland, this causes decrease of calcium reabsorption in the kidneys and GI tract as well as decrease in phosphate reabsorption. It also reduces calcium resorption and release of calcium from the bone.
Presentation of hypercalcaemia
- Mild = asymptomatic
- Severe = General malaise, depression, bone and abdo pain.
- Most severe = dehydration, confusion or cardiac arrest.
- Can also present with polyuria/nocturia due to calcium deposits in the kidney.
Investigations of hypercalcaemia
- Fasting serum calcium and phosphate samples.
- If serum phosphate is low = primary hyperparathyroidism. Normal/high = Other cause.
- Serum PTH = Normal/high = Primary hyperparathyroidism.
Management of hypercalcaemia
- Important to treat cause and decrease the calcium levels.
- If severe, the patient needs to be rehydrated, use bisphosphonates as well as prevent reoccurrence.
Definition of hypocalcaemia
- Calcium levels too low.
Aetiology of hypocalcaemia
- Increase in serum phosphate, reduced PTH function (thyroidectomy), vitamin D deficiency (UV light, malabsorption, antiepileptic drugs).
- CKD
How are calcium levels low/decreased?
- Decrease in PTH, leads to decrease calcium reabsorption, increase in renal phosphate, decrease in bone resorption and formation of active vitamin D - leading to calcium levels low.
Presentations of hypocalcaemia
- Increase in nerve/muscle excitability.
- Leading to numbness around the mouth and in the extremities followed by cramps.
- Chvaskeks (Tap over the facial nerve in the area of the parotid gland, would lead to ipsilateral facial nerve twitching) or Trousseuas sign for neuromuscular excitability.
Management of hypocalcaemia
- Acute = calcium gluconate.
- Peristent = vitamin D deficiency = ergocalciferol
How does PTH usually work?
- Normally PTH is released in response to low calcium levels.
- It is released from the parathyroid glands and is controlled by negative feedback.
Aetiology of primary hyperparathyroidism
- Solitary adenoma
- Parathyroid tumours.
Pathophysiology of primary hyperparathyroidism
- Inappropriate increase in PTH.
- PTH increases causing an increase in bone resorbtion and also decrease in bone absorption of calcium. It also causes increase renal and GI reabsorption of the calcium.
- Because calidriol can be converted into calcitriol in rapid amounts due to the PTH allowing 1 alpha hydroxylase to do this, this means that there is an increase in GI absorption of calcium but a decrease in phosphate reabsorption.
- Because the levels of calcium are so high this means that negative feedback loop doesn’t remain as tight and therefore PTH levels are allowed to remain high.
Investigations of primary hyperparathyroidism
- Calcium and PTH levels would be high while phosphate levels would be low.
Management of primary hyperparathyroidism
- Rehydrate the patient, give bisphosphonates to protect againt osteoporotic degeneration and prevent reoccurance (through avoiding diet high in calcium and vitamin D and also avoiding medications such as thiazide like diuretics).
- Possible parathyroidectomy or excision of the adenoma could be required - this would be done to avoid fractures or ulcers. But under certain criteria, including if the patient had both high serum and urine calcium levels, osteoporosis, bone disease, renal calculi or renal function and also if they were under 50.
Presentation of hyperparathyroidism
- Can be asymptomatic.
- Could present with depression, general malaise, abdo pain, bone pain, renal stones or osteoporosis/osteopenia.
Complications of hyperparathyroidism
- Hypoparathyroidism, recurrent laryngeal nerve damage and symptomatic drop in calcium.
Definition of hypoparathyroidism
- Decrease in the reduction in the amount of PTH or decrease in the activity of the PTH.
Pathophysiology of hypoparathyroidism
- Decreased PTH, leads to decreased bone resorption and increased bone reabsorption. Leads to decrease reabsorption within the kidneys but increase in phosphate. Decrease in the amount of calidriol into calcitriol leading to decreased reabsorption in the GI tract of calcium.
- All together decrease in calcium.
Defintion of primary hypoparathyroidism
- Decrease in the production of PTH due to the gland itself.
Aetiology of primary hypoparathyroidism
- Autoimmune diseases, Di George syndrome
Investigations of primary hypoparathyroidism
- Decrease in CA, but increase in phosphate levels.
Management of primary hypoparathyroidism
- Treat as hypocalcaemia.
- Use calcium gluconate and calcitriol.
Aetiology of secondary hypoparathyroidism
- Radiography, surgery (Parathyroidectomy or thyroidectomy) and hypomagnesium.
Defintion of pseudohypoparathyroidism
- Failure of target cells to respond to PTH due to resistance due to genetics.
Presentation of pseudohypoparathyroidism
- Short stature, round founds, short metacarpals, calcified basal ganglia and low IQ.
Investigations of pseudohypoparathyroidism
- Serum calcium is low but PTH is high.
Management of pseudohypoparathyroidism
- Same as primary hypoparathyroidism.
Definition of pseudopseudohypoparathyroidism
- Genetic but due to normal calcium levels.
Definition of hyperthyroidism
- Increased activity of the thyroid gland.
- Usually seen in women between the ages of 20 and 40.
Aetiology of hyperthyroidism
- Graves disease
- Toxic adenoma
- Toxic multinodular goitre
- Viral
- Post partum
Presentation of hyperthyroidism
- Weight loss, heat intolerance and irritability.
- Tremor, hyperkinesis, AF/Tachycardia, warm vasodilator peripheries and goitre.
- In terms of Graves, all of them above plus sweating as well as wide pulse, cardiac murmur, velvety skin.
Investigations of hyperthyroidism
- Increased T3/T4 levels and suppressed TSH levels.
- Increased TSH antibodies level if Graves disease is the aetiology.
- Can do thyroid ultrasound to identify different causes.
Management of hyperthyroidism
- Antithyroid drugs - Carbimazole - prevents the biosynthesis of thyroid stimulating hormone - but takes around 10 to 20 days to become therapeutic and therefore patients would require beta blockers for immediate symptom control.
- Radioactive iodine - Uptake and accumulation in the thyroid gland and begin local irradiation.
- Surgery - Thyroidectomy
Complications of hyperthyroidism
- Usually seen in older patients, including arrthymias, bone mineral loss, high output cardiac failure and thyroid storm.
How does T3/T4 normally get produced?
- The pituitary gland is stimulated to produced TSH, which cases the thyroid gland to produce T3/T4.
- Small amount of T3 is released from the thyroid gland, but most in the circulation is created by T4 being converted to T3 in the peripheral tissues.
- T3 and T4 circulate in the body bound to binding proteins, most commonly thyroxine binding globulin, with drugs and illnessess affecting the concentrations of these proteins.
Definition of hypothyroidism
- Under activity of the thyroid gland, meaning reduced production of T3 and T4.
- Usually seen in women and incidence increases with age.