Revision - Endocrinology Flashcards
What is congenital adrenal hyperplasia (CAH)?
Deficiency of 21-hydroxylase enzyme
This results in OVERproduction of androgens and UNDERproduction of cortisol & aldosterone.
How is CAH inherited?
Autosomal recessive
What is 21-hydroxylase enzyme responsible for?
Normally converts progesterone into cortisol & aldosterone.
Note - Progesterone is also used to create testosterone, but this conversion does not rely on the 21-hydroxylase enzyme.
Pathophysiology in congenital adrenal hyperplasia?
1) Defect in the 21-hydroxylase enzyme (this normally converts progesterone into aldosterone and cortisol).
2) There is extra progesterone floating about that cannot be converted to aldosterone or cortisol, so it gets converted into testosterone instead.
3) Result is low aldosterone, low cortisol and abnormally high testosterone.
4) Lots of ACTH secreted in response to low cortisol levels.
5) ACTH further stimulates the production of adrenal androgens
What is progesterone converted to in congenital adrenal hyperplasia?
Testosterone
Presentation of severe cases of congenital adrenal hyperplasia?
1) females can present at birth with virilised (‘ambiguous’) genitalia w/ enlarged clitoris - due to high levels of testosterone
2) hypoglycaemia, hyponatraemia, hyperkalaemia
This leads to:
- poor feeding
- vomiting
- dehydration
- arrhythmias
Define virilised
To assume masculine characteristics, as through a hormonal imbalance or hormone therapy.
When do mild cases of CAH typically present?
Patients who are less severely affected present during childhood or after puberty.
Their symptoms tend to be related to high androgen levels.
Presentation of mild CAH in females?
1) tall for age
2) deep voice
3) absent periods
4) acne
5) facial hair
6) early puberty
Presentation of mild CAH in males?
1) tall for age
2) deep voice
3) large penis
4) small testicles
5) early puberty
What is a key dermatological sign of CAH?
Skin hyperpigmentation (due to raised ACTH)
What investigation is used to confirm the diagnosis of CAH?
ACTH stimulation test
How can GH deficiency present in in neonates?
1) micropenis (males
2) severe jaundice
3) hypoglycaemia
What does a GH stimulation test involve?
Measuring the response to medications that normally stimulate the release of GH.
In GH deficiency, there will be a poor response to stimulation.
What medications are used in GH stimulation test?
I.e. which medications normally stimulate the release of GH?
1) glucagon
2) clonidine
3) arginine
Impact of glucagon on GH?
increases GH
Management of congenital GH deficiency?
1) daily SC injections of GH (somatropin)
2) treatment of other associated hormone deficiencies
3) close monitoring of height and development
What medication is used for GH replacement?
Somatropin
Features of adrenal insufficiency in neonates?
- lethargy
- vomiting
- poor feeding
- hypoglycaemia
- jaundice
- failure to thrive
Cortisol, ACTH, aldosterone & renin levels in Addisons vs 2ary adrenal failure?
Addison’s:
- low cortisol
- raised ACTH
- low aldosterone
- high renin
2ary adrenal failure:
- low cortisol
- low ACTH
- normal aldosterone
- normal renin
What test can be used to confirm adrenal insufficiency?
Short Synacthen Test (ACTH Stimulation Test)
What short synacthen test result indicates 1ary adrenal failure?
Failure of cortisol to rise more than double the baseline
How is congenital hypothyroidism often diagnosed?
Newborn blood spot screening test
What are some signs that may be picked up on examination in congenital hypothyroidism?
Poor growth
Macroglossia
Myxedema
Large fontanelles
Hypotonia
Bradycardia
Distended abdomen with umbilical hernia
Goitre
If there is a suspicion of cerebral oedema following DKA treatment, what is the investigation?
CT head
Management options for cerebral oedema 2ary to DKA treatment?
1) slow fluids
2) iv mannitol
3) iv hypertonic saline
What type of fluid therapy is given in cerebral oedema?
HYPERtonic –> reduces ICP
How much 0.9% saline should be given to children with DKA as an initial bolus:
a) for children in shock
b) for children not in shock
a) 20ml/kg of 0.9% sodium chloride over 15 minutes
b) 10mL/kg 0.9% sodium chloride over 1 hour
