Endocrine Flashcards
What is the name of the diagnostic criteria for DM?
Draw the table of details
American Diabetic Association
- Fasting plasma glucose
- > = 7: DM
- 5.6~7: IFG
- 2h post-OGTT glucose / Random plasma glucose
- > = 11.1: DM
- 7.8~11: IGT
(5678, 711)
- HbA1c
- > =6.5%: DM
Time of fasting for fasting plasma
> =10h
Procedure for 2h post-OGTT plasma glucose
overnight fasting >=8h
1. Record plasma glucose at t0
2. Drink 75g anhydrous glucose in 300ml water in 10 mins
3. Sit quietly and check at 120min (additional check at 60min in case of pregnancy)
FP and FN of HbA1c results (4+3)
FP: splenectomy, pregnancy, IDA, prolonged aspirin intake
FN: splenomegaly, haemolytic anaemia, anti-oxidant
Alternative for HbA1c
Fructosamine (reflect 1~3 weeks)
Gestational diabetes diganosis by OGTT
[t0]
5.1~6.9: GDM
>=7: DM
[60min]
>=10: GDM
[120min]
8.5~11: GDM
>=11.1: DM
(511085)
Complications of gestational diabetes (2)
macrosomia –> difficult labour
faetal hyperinsulinaemia –> neonatal hypoglycaemia
Monitoring of glycation level for DM patients (3)
Point-of-care glucometry
Lipid profiles
Albuminuria & GFR
ADA therapeutic goals for DM patients
(HbA1c, pre-prandial BG, post-prandial BG, SBP, DBP, TG, LDL-C, HDL-C)
<7%
5~7.2
<10
<130
<80
<1.7
<1.8
>1.1 for male, >1.3 for female
Vascular complications of DM (6)
retinopathy, neuropathy, nephropathy
cerebrovascular disease, CAD, PVD
2 ketones and their formation in DKA
acetoacetate, beta-hydroxybutyrate
↓ insulin/glucagon ratio –> ↑ lipolysis & FA oxidation –> ketoacids
Precipitating factors of DKA / HHS (2)
stress
discontinued injection of insulin
HHS full form
Hyperosmolar hyperglycaemic state
Na and K status in DKA / HHS
early hypoNa, late hyperNa
N or hyperK but total K deficit
Explain for the hyperK in DKA
ICF to ECF shift caused by insulin deficiency & hyperosmolality
Whipple’s triad
- plasma glucose <=2.5 by laboratory method
- hypoglycaemic symptoms
- symptoms relief after elevation of plasma glucose
Aetiology of hypoglycaemia (fasting, reactive)
Fasting:
- excessive utilization: insulin administration, oral hypoglycaemic, insulinoma, extra-pancreatic tumours
- diminished glucose production: adrenal insufficiency, GH deficiency, liver disease, renal disease, autoimmune cause
Reactive:
- post-gastrectomy syndrome
Others: alcohol
Further testing for fasting hypoglycaemia (4)
Serum insulin
C-peptide
IGF-2, IGFBP3
Triple function test for pituitary deficiency
- insulin tolerance test
- GnRH stimulation test
- TRH stimulation test
Hyperprolactinaemia DDx
Physiological: pregnancy, stress
Primary: Prolactinoma
Secondary: NFPAH, dopamine depleting / receptor blocking agents, hypothalamic disease
Tertiary: Primary hypothyroidism
Others: chronic renal failure, liver cirrhosis
Free androgen index
= T/SHBG *100
> =5: hyperandrogenaemia
Klinefelter syndrome
47, XXY (primary hypogonadism in men)
Turner syndrome
45, X (primary hypogonadism in women)
Kallmann syndrome, Prader-Willi syndrome
hypogonadotrophic hypogonadism
Aim for progesterone withdrawal test
investigation of amenorrhoea
Iodine deficiency and excess aetiology (2+3)
Deficiency: pregnancy, malnutrition
Excess: contrast, amiodarone, eye drops & ointments
Jod-Basedow effect
failure to downregulate NIS in iodine excess –> hyperthyroidism
Wolff Chaikoff effect
iodine exposure –> inhibit iodide organification
Failure of escape –> hypothyroidism
Anti-thyroid antibodies involved in Dx of Hashimoto thyroiditis (2)
Anti-Tg Ab
Anti-TPO Ab
Anti-thyroid antibody involved in diagnosis of Graves disease
Thyoid stimulating IgG (TSI)
3 MC causes of hyperthyroidism
- Graves’ disease
- Toxic multinodular goitre / Plummer’s disease
- Toxic adenoma
Anti-thyroid drugs (2): mechanisms, preference
Carbimazole, Propylthiouracil
Mechanisms: inhibit TPO, iodination, coupling (PTU inhibits peripheral conversion of T4 to T3)
Preferences: PTU in pregnancy and thyroid storm
Which iodine is used for thyroid scan? Which is used for radioactive iodine treatment?
I-123
I-131
Management of hypothyroidism and monitoring (2)
L-thyroxine
Monitoring: TSH, cortisol
3 zones of adrenal cortex
zona glomerulosa, zona fasciculata, zona reticularis
Screening test for Cushing syndrome (3)
- Overnight dexamethasone suppression test
- 24h urine free cortisol
- Late night salivary cortisol
RR for insulin
<3
RR for C-peptide
<0.6
Discriminatory tests for Cushing syndrome (3)
- Plasma ACTH
- High dose dexamethasone suppression test
- CRH stimulation test
Interpretation of high dose dexamethasone suppression test
50% suppression ==> pituitary problem
⨉ suppression ==> ectopic ACTH
MC cause for renal artery stenosis in young patients
fibromuscular dysplasia
Gene for apparent mineralocorticoid excess (AME) (pathogenesis)
HSD11β2
↓ 11β-hydrosteroid dehydrogenase type 2 –> ↑ cortisol binds to mineralocorticoid receptors –> pseudohyperaldosteronism
Confirmatory test for hyperaldosteronism
Salt loading test / saline suppression test / captopril test
Salt loading test: measurement (2, RR)
urine aldosterone (<38)
urine Na (>200)
Discriminatory tests for hyperaldosteronism
(Interpretations)
- Spot aldosterone-renin ratio
- ↑ : primary
- N/ ↓: secondary
- Postural test
- physiological rise: bilateral adrenal hyperplasia
- paradoxical fall: Conn’s syndrome
Test for adrenal insufficiency (Interpretation)
Short synacthen test
a. cortisol rise <200 above baseline: primary cause
b. cortisol rise >200 above baseline with level <500: secondary cause
c. cortisol rise >200 above baseline with level >550: normal
MC congenital adrenal hyperplasia
21-hydroxylase deficiency
RR for overnight dexamethasone suppression test
<50
Screening tests for suspecting phaeochromocytoma (3) and the second line test for borderline results
- 24h urine catecholamines, metanephrine, VMA
- Plasma catecholamines
- Plasma metanephrines
- Overnight clonidine suppression test
Overnight clonidine suppression test interpretation
NA/Cr >60 or adrenaline /Cr >20 : phaeochromocytoma
Investigation for midgut carcinoid tumour
urine 5-HIAA
Side effects of anti-thyroid drugs
Allergy, agranulocytosis, hepatotoxicity
What is the HVA/VMA ratio that indicates a poor prognosis for neuroblastoma?
<1
Secretion of carinoid tumour in different regions
Foregut: 5-HT, His
Midgut: serotonin
Hindgut: /
Metabolic pathways of tyrosine & tryptophan
tyrosine => DOPA => dopamine => NA => A
- D => HVA
- NA => notmetanephrine => VMA
- A => metanephrine => VMA
tryptophan => 5-HT => serotonin => 5-HIAA
Which CAH leads to androgen deficiency?
17α hydroxylase deficiency
How does DM lead to abnormal lipid profile?
High VLDL —> high TG —> high LDL-C —> low HDL-C
- hyperinsulinemia & hyperglycaemia → + hepatic VLDL synthesis → ↑ hepatic release of TG & LDL
- insulin resistance → ↓ inhibition of lipolysis in adipocytes
- insulin resistance → ↓ lipoprotein lipase activity of muscles and adipocytes
Why urine ketostix could be negative in severe DKA?
↑ NADH/NAD ratio → acetoacetate converts to β-hydroxybutyrate → FN in urine ketostix
Examples of extra-pancreatic tumour that leads to tumour-associated hypoglycaemia (2)
retroperitoneal fibrosarcoma, hepatoma
How does liver disease lead to hypoglycaemia?
↓ glycogen reserve
How does renal disease lead to hypoglycaemia?
multifactorial
uraemia –> inhibit liver gluconeogenesis & lead to poor appetitie
↓ insulin clearance
2nd causes of hyperaldosteronism (3)
renal artery stenosis
juxtaglomerular apparatus tumour
renin-secreting tumour
How does DM lead to atherosclerosis?
apoB glycation –> ↓ affinity of LDL to LDL-R –> ↓ LDL catabolism –> ↑ LDL in circulation –> atherosclerosis
normal GH response in glucagon stimulation test
up to 20 ng/mL
FP for 24h urine catecholamine, metanephrine, VMA (4)
medications (e.g. β blockers, α blockers…), food (e.g. caffeine, tobacco), physical stress, OSA
Why is glucagon stimulation test not used anymore for phaeochromocytoma?
hypertensive crisis risk
Risk for overnight clonidine suppression test
hypotensive crisis
Compare pros and cons between urinary and plasma metanephrines (3+4)
Urine:
a. Pros:
- well-established, widely available
- urinary conc. make analysis relatively easy
- easy to implement
b. Cons:
- 24h collection inconvenient for patients
- reliability problem
- difficult to control dietary & daily life influence
- inappropriate for patients with renal failure
Plasma (the opposite)
Why genetic testing should be considered in all patients who present with PPGL? (3)
- > = 1/3 of all patients with PPGLs have disease-causing germline mutations
- mutations of SDHB lead to metastatic disease commonly
- earlier diagnosis & treatment of PPGLs & other manifestations in relatives
Suppression test for high prolactin level
Bromocriptine suppression test
DDx for high testosterone level (in female) (3)
polycystic ovarian syndrome
Cushing syndrome (active adrenal)
ovarian tumour
How does hypothyroidism lead to high lipid profile?
low LDL-R & lipoprotein lipase activity –> LDL cannot be recycled back to liver –> ↓ LDL metabolism —> remain in circulation –> ↑ cholesterol
Confirmation laboratory test for GH secreting tumour
IGF-1
Management of DKA / HHS (5)
Insulin
Rehydration
KCl
Close monitoring
Treat underlying cause