MRCP Endocrine Flashcards
What is a differential in young women presenting with prolonged amenorrhoea? What test would you order (after b-hcg/TFTs etc)
premature ovarian failure
FSH
The suspicion here, given the prolonged cessation of menses with a normal weight, normal thyroid function tests, and a past history of coeliac disease is premature ovarian failure, thought to be autoimmune in origin. As such looking for elevated FSH (28 is the upper limit of normal, 40 is the value required to confirm menopause) is the optimal next investigation.
Unfortunately spontaneous return of ovarian function is extremely rare. Therefore this patient in all likelihood should be offered hormone replacement therapy.
Which technique is the best in differentiating between ectopic Cushing’s syndrome and pituitary dependent Cushing’s disease?
Inferior petrosal sinus sampling is an extremely sensitive, specific and accurate test for differentiating between Cushing’s disease and ectopic ACTH production.
A raised ACTH from here compared to the periphery suggests a pituitary cause.
Features of zinc deficiency
- dwarfism
- hypogonadism
- hepatosplenomegaly
- rough and dry skin
- mental lethargy, and
- geophagia
- Hypertelorism
What do thyroid hormones enhance?
- insulin-dependent entry of glucose into cells
- myocardial oxygen consumption
- nerve conduction
- gluconeogenesis, and
- oxidation of fatty acids.
Who should be screened for thyroid abnormalities?
- Patients with atrial fibrillation
- Patients with hyperlipidaemia (4–14% have hypothyroidism)
- Diabetes mellitus—on annual review
- Women with type 1 DM during 1st trimester and post delivery (3-fold rise in incidence of postpartum thyroid dysfunction)
- Patients on amiodarone or lithium (6 monthly)
- Patients with Down’s or Turner’s syndrome, or Addison’s disease (yearly)
Eye signs seen in graves disease only
- Soft-tissue signs: periorbital oedema, conjunctival injection, chemosis
- Proptosis/exophthalmos
- Diplopia/ophthalmoplegia
- Optic nerve compression causing visual failure
Example of Meglitinides
Repaglinide
Nateglinide
MoA of meglitinides
increase pancreatic insulin secretion
like sulfonylureas they bind to an ATP-dependent K+(KATP) channel on the cell membrane of pancreatic beta cells
How do Raloxifine and Tamoxifen differ?
Tamoxifen (another SERM) acts as a partial agonist at the endometrium, so can promote endometrial hyperplasia.
Raloxifene acts as an oestrogen agonist at some sites, for example, bone to increase mineralisation, but acts as an antagonist at other sites, for example, uterus/breast (preventing endometrial/breast hyperplasia).
It differs from tamoxifen in this regard, because tamoxifen (another SERM) acts as a partial agonist at the endometrium, so can promote endometrial hyperplasia.
If cortisol is not suppressed by the low or high dose dexamethasone suppression test
Primary adrenal Cushing’s syndrome (low/undetectable ACTH) or
Ectopic ACTH is the cause (high ACTH)
How does PTH increase calcium?
Enhances the release of calcium from bones by binding to osteoblasts which stimulates the formation of osteoclasts
Enhances reabsorption of calcium in the distal tubules.
Which kind of cancer is associated with acromegaly?
Carcinoid tumour
ectopic GH-releasing hormone
Features of McCune-Albright syndrome
- Precocious puberty
- Bony fibromas leading to possible pathological fractures
- Thyrotoxicosis
- Café au lait spots
- Polyostotic fibrous dysplasia
- Short stature
McCune-Albright syndrome: cause?
Random, somatic mutation in the GNAS gene
**not inherited
How does Amiodarone cause hypothyroidism
Stops peripheral conversion of t4–>t3
REM: thyroid mainly makes t4 -relies on peripheral conversion
DKA blood gas features?
hyperglycaemia
lactic acidosis
low bicarbonate
What are the effects of Exenatide
Suppresses appetite
Inhibits glucose production in the liver
Slows gastric emptying
Stimulates insulin release
mimics the effect of the gut hormone GLP-1 (glucagon-like peptide 1)
What would you see on the gas of a patient with Cushings syndrome?
Metabolic alkalosis
By which mechanism does Cushings lead to a metabolic alkalosis
Excess ACTH production leads to upregulation of corticosteroid production, increase in mineralocorticoid production, and consequent hypokalaemia with metabolic alkalosis.
Which gene mutations is Monogenic diabetes/MODY associated with
glucokinase and HNF1a and HNF4a
What is the incretin effect?
glucose given via the gut will elicit a greater insulin response than IV
glucose-dependent insulinotropic hormone (GIP) and glucagon-like peptide-1 (GLP-1)
What is acarbose
alpha glucosidase inhibitor which inhibits the splitting of disaccharides into glucose and so inhibits glucose absorption from the gut
Why is there an increased risk of hypoglycaemia in patient with renal impairment taking glibenclamide?
two active metabolites, 4-trans-hydroxyglibenclamide and 3-cis-hydroxyglibenclamide, which are both renally excreted
What is the significance of 21 hydroxylase ?
An enzyme involved in the cholesterol steroid pathway
Anti-21-hydroxylase antibody is found in 80% of patients with autoimmune adrenalitis
