Endocrinology Flashcards
What are the causes of hyerpnatraemia (name 5)?
1) Insensible loss in unconscious patient, e.g., sweating, vomiting, burns.
2) Diabetes Insipidus.
3) Osmotic coma, e.g., diabetic coma.
4) Conn’s syndrome (hyperkalaemic acidosis)
What are the symptoms of hypernatraemia (4)?
- Thirst
- Confusion
- Coma
- If severe, cerebral haemorrhage or thrombosis may occur.
How should hypernatraemia be Rx?
Dehydration and low sodium should be corrected slowly, over a 48 hr period at least. The more extreme the derangement, the slower this should be. Oral rehydration is preferable, but often has to be IV.
If IV fluids are used to correct a high sodium, what fluid should be used?
Ongoing debate! Some clinicians use 5% dextrose (guided by repeated sodium levels and urine output), others use 0.9% saline (as this is hypotonic in a hypernatraemic patient).
What is the result of excessively rapid rehydration of someone with hypernatraemia?
It can result in cerebral oedema.
What are the causes of cerebral oedema? (List 5)
1) Acute hepatic failure.
2) Benign intercranial hypertension.
3) Raye’s syndrome.
4) Excessive fluid infusion in a dehydrated/hypernatraemic patient.
5) Poor fluid management in someone with hyponatraemia.
How does cerebral oedema appear on a CT?
As a hypodense area.
Different forms of cerebral oedema are described (not caused!) what are they?
1) Vasogenic - caused by excessive protein-rich fluid leaking into the extracellular space through damaged capillaries. It especially affects white matter. Sometimes it can be Rx with corticosteroids.
2) Cytotoxic - damage to neurones and glial cells leads to leakage.
3) Interstitial - CSF leaks into the extracellular space, e.g., non-communicating hydrocephalus.
At what pressure do clinical signs of cerebral oedema start to appear?
Around 30 mm Hg
What happens if the process of cerebral oedema is not arrested?
Respiratory arrest and death from brainstem coning occurs.
What device is sometimes used to anticipate and prevent the bad consequences of developing cerebral oedema?
ICP bolt - inserted by the neurosurgeons, and managed by ITU.
What is a normal cerebral pressure, i.e., when no cerebral oedema is present , if a bolt were inserted, what would the pressure be?
0-1mm Hg
Other than bolts, what treatments exist for cerebral oedema?
Mannitol used to be used. It is not routinely used anymore as it can possibly result in reduced cerebral perfusion. It is also potentially nephrotoxic, so UO must be monitored hourly.
Steroids are sometimes used in certain circumstances.
Barbituates (e.g., theiopentone) - however may cause haemodynamic disturbances and mask the clinical effects of cerebral oedema.
When might steroids be used to treat cerebral oedema?
Only if the cerebral oedema is secondary to tumour or abscess but never due to trauma.
How should patients with cerebral oedema be positioned?
Flat, or with the head raised no more than 30 degrees from the horizontal, as further elevation produces paradoxical elevation in ICP.
How can control of respiration be used to treat cerebral oedema?
Hyperventilation - reduces PCO2 to 3.5 Pa as this causes vasoconstriction and may reduce cerebral oedema.
What is galactosaemia?
A rare autosomal recessive condition caused by the absence of an enzyme, galactose-1-uridyl transferase. This results in the accumulation in cells of galactose-1-phosphate, which is highly toxic. The incidence in the UK is about 1/60,000.
If an infant is normal at birth, but on commencement of milk feeds they suffer from 4 complaints, what should be suspected? What are those 4 complaints?
Jaundice, vomiting, diarrhoea, and failure to thrive.
The condition is galacotsaemia.
It can result in cataract formation (it is one of the causes of bilateral cataracts in infants), psychomotor retardation, hepatosplenomegally, renal disease, increased susceptibility to infection, and hypoglycaemia after exposure to galactose in the diet.
If galacotsaemia is suspected in a newborn, what investigations would support the diagnosis?
Raised plasma galactose.
Galactosurea.
Aminoacidurea.
What proportion of premenopausal women have hirsuitism? What is the most common cause?
1 in 10!
Most common cause is PCOS, but there are lots of others, so important to stay alert to other possibilities.
What are the possible causes of hirsuitism? (12)
1) Idiopathic
2) PCOS (over 70% of cases)
3) Menopause/primary ovarian failure.
4) Congenital adrenal hyperplasia.
5) Pituitary tumours: Cushing’s disease, acromegaly, hyperprolactinaemia.
6) Cushing’s syndrome.
7) Androgen-secreting tumours: adrenal, ovarian.
8) Insulin resistance syndrome.
9) Hypothyroidism.
10) Obesity.
11) Porphyrias.
12) Medications, e.g., steroids, sodium valproate, phenytoin, danazol, minoxidil, progestogens.
What is minoxidil?
Topical minoxidil is used sometimes in the treatment of androgenic alopecia. It causes hair growth. (It is one of the causes of hirsuitism).
It mode of action involves dilation of arterioles.
Results of the use of the drug are variable, and it often has to be continued for long periods.
What is danazol? What is it used for? (2 main uses)
A testosterone derivative which suppresses the LH surge, inhibits ovarian steroid genesis, reduces plasma levels of sex hormone binding globulin (and therefore increases levels of free, unbound testosterone).
The main use is in endometriosis, where it creates a high androgen, low oestrogen environment which does not support the growth of endometriosis. Usually used for 6-9/12.
The other use is in the prophylaxis of hereditary angioneurotic oedema
What are the characteristics of idiopathic hirsutism?
What is it thought to be caused by?
What ethnicities are most effected?
Regular menstrual cycles are maintained, and there are no other features of androgen excess.
It is thought to be due to an increased sensitivity to androgens.
This type of hirsutism has been reported within families (I.e., likely a genetic element), and is more common in South Asian and Mediterranean ethnicities.
What is the most common cause of hirsutism?
What percentage of hirsutism does it account for?
What percentage of the population does it affect?
PCOS.
It affects 5-10% of premenopausal women.
It accounts for 70% of hirsutism.
What criteria is used to diagnose PCOS, and what are the criteria?
Although there are several criteria, the system that seems most widely adopted is the Rotterdam Criteria.
To qualify as having PCOS, a women must have two out of three of:
1) Ultrasound evidence of polycystic ovaries.
2) Oligomenorrhea (cycle length of 35 days or more) and/or presence of anovulation (for 6 months or more).
3) Clinical and/or biochemical signs of hyperandrogenism.
Other than hirsutism, what are the features of hyperandrogenism? (6)
1) Deep voice.
2) Frontal balding.
3) Cliteromegally.
4) Acne.
5) Increased libido.
6) Malodorous perspiration.
When taking a history of someone with hirsutism, what points should be covered? (9)
1) When the symptoms were first noticed, and age of onset.
2) Features of hyperandrogenism.
3) Areas where hair growth has been noted.
4) How quickly the hair growth has progressed.
5) What methods have been used to control hair growth.
6) Obstetric history (e.g., previous pregnancies, infertility).
7) Menstrual history (age of menarchy, regularity of cycle, possibility of pregnancy, last menstrual period).
8) Any recent change in weight.
9) Medications.
Why does obesity implicated in PCOS - I.e., making it worse, or maybe even triggering it?
Obesity leads to increased insulin resistance, which in turn leads to hyperinsulinaemia.
High levels of insulin have two relevant consequences in this context:
1) High insulin levels encourage the theca cells of the ovaries to produce more androgens.
2) They also cause the liver to produce lower amounts of sex hormone binding globulin-this leads to increased levels of free testosterone (though total levels of testosterone may in fact stay the same).
When considering a diagnosis of hirsutism, what alternative diagnosis should be considered and rejected before beginning to go down the “hirsuitism” path?
How can you differentiate the two?
What, in a general sense, causes hirsutism? (Although, of course, there are many possible sub-causes).
Hirsutism (in general terms) is caused by either an over-production of androgens or an increased sensitivity to them, causing MALE PATTERN HAIR GROWTH.
It should NOT be confused with hypertrichosis, which involves a general excess of hair in a non-androgen distribution, and has a different aetiology.
What is the typical age of onset of hirsuitism?
If it occurs in an infant or a pre-pubescent, is this potentially more or less serious? And what possible causes should be considered in this case?
The typical age of onset can vary from 15-35; it often first appears at the time of puberty and tends to worsen gradually over time.
In an infant or prepubescent, it should be taken MORE seriously; possible causes include hypothyroidism, congenital adrenal hyperplasia, or precocious pubity.
What are the two types of human hair and where are they found?
In hirsutism, which type shows excessive growth.
1) Terminal - dark, course, and thick - typically found on the scalp, eyebrows, eyelashes, and - after puberty - around the groin and axilary areas areas.
2) Vellous hair - soft and brown - covers the rest of the body, except for the palms of hands, soles of fees, and lips.
Hirsutism is the excessive growth of the terminal hair type in females.
Where does hirsutism typically affect, I.e., what areas of the body?
It follows an androgen-dependant (I.e., male) distribution pattern. Face, upper list, chin, chest (including areola), lower abdomen (including linea alba). Also the anterior thighs and buttocks.
Amount of hair depends on the individual and their family, and their ethnic group.
What ethnic groups tend to be more or less affected by hirsutism?
More common - South Asia and Mediterranean ethnicities.
Rarer in - East Asia and sub-Saharan Africa.
What is congenital adrenal hyperplasia (CAH)?
It is an autosomal recessive disorder in which cortisol production is impaired.
How does congenital adrenal hyperplasia present classically and non-classically?
Classical presentation is in childhood with - ambiguous genitalia in girls or precocious pubity.
Non-classic or adult onset CAH is milder - it tends to be picked up in adults, with symptoms of glucocorticoid deficiency and is often noted due to hirsutism. It often mimic PCOS. It is a milder phenotype.
What is the risk of Caucasians developing CAH? What ethnic groups have a higher risk, and by how much?
The risk generally is low - about 0.2-0.3%.
However some populations have a tenfold increased risk these are Ashkenazi Jews, Southern Meddetarranians, and Eastern Europaeans.
In what group of women may identifying Congenital Adrenal Hyperplasia be of especial use, and why?
Women who are trying to get pregnant; this is because treatment with glucocorticoids can reduced the chance of miscarriage.
As this is a genetic condition, pre-conception genetic councils sling Maui be appropriate.
What are androgen secreting tumours, and where do they arise?
Common or rare?
Why is it important to rule out this diagnosis?
It is a tumour of the ovary or testes that secretes androgen.
A cause of hirsutism in women.
It is rare - only about 0.2% of androgen disorders in women - but important to rule out as HALF these tumour are malignant.
What features would make me think, “hang on one damn second - what is this lovely patient sitting on front of me has an androgen secreting tumour?”
What initial hormonal investigation would add weight to this diagnosis?
You should consider it in people presenting with a RAPID ONSET of hirsutism or virilisation, especially just after puberty.
Initially, test FSH and LH - they are both low in CAH.
In AST, testosterone levels are high at 1.5-2x the normal level. Other androgens in the sex steroid genesis pathway are used to help distinguish between CAH and AST.
Why does hypothyroidism lead to hirsutism?
1) It can cause dry, brittle hair that snaps easily.
2) It can include the ratio of anagen to telogen phases (telogen is the phase in hair growth where there is resting of hair production)! While anagen is the active, hair-growing phase)
3) It can reduce the production of SHBG and therefore increase the level of circulating free testosterone.
What is hyperandrogenic insulin resistant acanthosis nigricans (HAIR-AN) syndrome?
It is a inherited condition that may present with features of PCOS.
Severe insulin resistance causes high circulating levels of androgens, which in turn causes acanthosis nigricans. Virilisation may be a feature.
Both insulin resistance and hirsutism may occur and be very difficult to treat in this group.