ENDOCRINE: Electrolyte abnormalities incl parathyroid Flashcards
SIADH, calcium NEED TO ADD MORE ON PARATHYROIDISM
What is the relevance of hyponatraemia?
Very commonly affects hospital patients, up to 30% of hosp patients will have hyponatraemia
Hyponatraemia is characterised by a low concentration of sodium in the serum, specifically less than 135mmol/L.
What are the symptoms of hyponatraemia?
Early symptoms: headache nausea vomitting general malaise
Later signs:
confusion
agitation
drowsiness
What serious symptoms can acute severe hyponatraemia cause?
Seizures
Resp depression
Coma
Death
What common medication can cause hyponatraemia?
thiazide like diuretics
ACEi
SSRIs
Furosemide
What is osmolality?
How salty the blood is, low osmolality means less salt
What is a complication of acute severe hyponatraemia?
cerebral oedema
In patient with severe acute hyponatraemia what would always prescribe?
Hypertonic saline
What are the hallmark biochemical features of primary adrenal failure?
Hyperkalaemia, hyponatraemia, raised urea and mild anaemia, hypoglycaemia
What biochemical investigations would you do in a patient with hyponatraemia?
Serum osmolality, urine osmolality, urine sodium, thyroid function and assessment of cortisol response
What is the first thing to do if a patient presents with low serum osmolality?
Rule out non-hypo- osmolar hyponatraemia e.g. hyperglycaemia
What would a low serum osmolality and urine osmolality of less than 100mosmol/kg indicate?
primary polydipsia or inappropriate IV fluid administration
What is the next steps in investigation if a patient has low serum osmolality and a urine osmolality of greater than 100mosmol/kg?
You need to measure their urine sodium
What would a low serum osmolality and a urine osmolality of greater than 100mosmol/kg (100= concentrated) and urine sodium of less than 30mmol/kg?
True dehydration e.g. GI salt loss
OR
clinically overloaded but intravascular depletion e.g. in congestive cardiac failure, cirrhosis or nephrotic syndrome
Urine sodium of <30 mmol/L suggests low effective arterial volume
What would a patient with SIADH look like biochemically (serum osmolality, urine osmolality, urine sodium and their fluid balance)
Low serum osmolality
Urine osmolality> 100mosmol/kg
Urine sodium> 30mmol/L
Euvolaemic
What is the next steps in investigation if a patient has low serum osmolality and a urine osmolality of greater than 100mosmol/kg and urine sodium of greater than 30mmol/kg?
Need to work out - are they EUVOLAEMIC or DEHYDRATED?
A patient low serum osmolality and a urine osmolality of greater than 100mosmol/kg and urine sodium of greater than 30mmol/kg and they are dehydrated, what do you need to consider?
Addison’s disease, renal or cerebral salt wasting or does the patient have a history of vomitting
What do you need to rule out before you make a diagnosis of SIADH?
Hypothyroidism - elevated ADH due to decreased Cardiac output
Total salt depletion
ACTH deficiency- check serum cortisol as low cortisol causes less -ve feedback on CRH and Cortisol directly suppresses ADH secretion )
Why does ACTH deficiency present like SIADH?
Cortisol deficiency leads to increased ADH secretion
What are the causes of SIADH?
- Pituitary tumour
- Tumours: small cell lung cancer, thymoma, lymphoma
- Pulmonary disease: infections, pneumothorax, asthma, cystic fibrosis
- CNS disease: infection (SE of meningitis/encephalitis), head injury
- Drugs: chemotherapy, psychiatric drugs (lithium = nephrogenic cause)
- Idiopathic
What malignancy is know to cause SIADH?
small cell lung cancer
How do you treat SIADH?
Fluid restriction- however in practice this is quite poorly tolerated
ADH antagonists- Tolvaptan
Demeclocycine- tetracycline antibiotic that inhibits ADH
How do you treat hyponatraemia?
Hypovolaemic hyponatraemia- normal saline
Hypervolaemic hyponatraemia- needs specialist treatment to treat the underlying cause of CCF, nephrotic syndrome or cirrhosis
What is Trousseau’s sign? What is relevance?
Due to Hypocalcaemia
When inflate BP cuff above systolic pressure. Brachial artery is occluded. Causes carpal spasm (e.g. wrist flexing and fingers abducting)
What is Chvostek’s sign? What is its relevance?
Due to hypocalcaemia.
Tapping over parotid (CN7) causes facial muscles to twitch
Define hypoparathyroidism
- medical condition characterized by abnormally low levels of parathyroid hormone (PTH)
- this leads to disturbances in calcium and phosphorus metabolism.
- It can be primary (due to parathyroid gland dysfunction) or secondary (resulting from other medical conditions or treatments).
Risk factors for Hypoparathyroidism
- Neck surgery or radiation therapy involving the parathyroid glands.
- Autoimmune conditions, such as autoimmune polyendocrine syndrome.
- Genetic factors and familial forms of the condition
Pathophysiology of hypoparathyroidism?
- Decreased PTH production or function > disrupts calcium and phosphorus homeostasis.
- This leads to decreased calcium absorption from the intestines, reduced bone resorption, and impaired renal reabsorption of calcium.
What are the main symptoms of hypoparathyroidism?
- Hypocalcemia-related manifestations: muscle cramps, perioral and others paresthesias, tetany, and seizures.
-Trousseau’s sign: carpal spasm if the brachial artery occluded by inflating the blood pressure cuff and maintaining pressure above systolic
-Chvostek’s sign: tapping over parotid causes facial muscles to twitch
- Neuropsychiatric symptoms: anxiety, depression, and cognitive impairment
- Ocular symptoms: cataracts (chronic hypoparathyroidism) and impaired night vision
- Dental abnormalities: dental enamel hypoplasia and tooth discoloration
Differenicals for hypoparathyroidism?
Distinguishing hypoparathyroidism from other medical conditions with similar symptoms is essential, including:
- Hypocalcemia due to other causes (e.g. renal failure)
- Vitamin D deficiency
- Neuromuscular disorders
- Psychiatric conditions
Diagnostic investigations for hypoparathyroidism?
- Serum calcium (low) and phosphate levels (high)
- Measurement of PTH levels (low/inappropriately normal)
- Assessment of vitamin D status
- Urinary calcium may be low
- ECG to detect cardiac abnormalities due to hypocalcaemia - prolonged QT
Management of hypoparathyroidism?
- Oral calcium and active vit D (calcitriol) to maintain low-normal calcium levels. This is to avoid renal complications
- Regular Monitoring: Ongoing monitoring of calcium levels and PTH
- Addressing Symptoms: Symptomatic management of neuromuscular and psychological symptoms
- Potential Surgery: Parathyroid gland autotransplantation or glandular tissue implantation in refractory cases
- In acute severe hypocalcaemia, treatement with IV calcium may be required
Complicaitons of hypoparathyroidism?
- Severe hypocalcemia leading to seizures and cardiac arrhythmias
- Kidney stones due to increased urinary calcium excretion
- Impaired renal function
- Cataracts
- Neurological and neuropsychiatric sequelae
What is Pseudohypoparathyroidism?
how is this different from hypoparathyroidism?
- Rare genetic disorder where the target organs (bone, kidney, and gut) fail to respond to normal levels of parathyroid hormone due to defects in the PTH receptor.
- This is in contrast to hypoparathyroidism, in which there is a deficiency of the parathyroid hormone itself.
Cause of Pseudohypoparathyroidism
Pseudohypoparathyroidism is most commonly due to mutations in the GNAS1 gene, which codes for the alpha subunit of the Gs protein. This protein is vital for PTH to exert its action on its target cells.