Endocrine

Question 1

Name 4 tests to screen for Down syndrome (4)
What if one of them is abnormal? (1)

Answer 1

Low free E3, low AFP, high hCG, and high inhibin A
Proceed to karyotyping or FISH

Question 2

Name a test to screen for pituitary tumour (1)
What are clinical signs? (2)

Answer 2

prolactin >5X
Amenorrhea & galactorrhea

Question 3

Name a test to screen for Gastrinoma (1)

Answer 3

Gastrin >10X

Question 4

Name common cancer occurs in Multiple endocrine neoplasia
MEN1 (2)
MEN2 (2) MEN2B (1)

Answer 4

MEN1: Parathyroid gland (High Cai) > pancreas (gastrin)
MEN2: pheochromocytoma and thyroid carcinoma
MEN 2B: neurofibroma

Question 5

Describe hormone levels in menopausal women (4)
What is the most important lab finding to determine if a women is menopausal? (1)

Answer 5

The problem of menopause is the limitating follicle, leading to decrease estrogen level
FSH increase by negative feedback of estrogen such that FSH>LH
High LH causes Theca cells to release testosterone

Most important finding is High FSH

Question 6

Explain lab findings in PCOS. (4)
[FSH Low, LH High, testosterone High, progesterone Low]
Describe one complication of PCOS. (1)
Why are there cysts in PCOS? (1)
How to treat PCOS? (2)

Answer 6

1.The problem of PCOS is high GnRH release, leading to reduced FSH & increased LH release
2.High LH causes Theca cells to release testosterone (hirsutism)
3.Low FSH level is insufficient for ovulation
4.In the absence of corpus luteum, there is no release of progesterone
5.low progesterone leads to high GnRH release, repeating the cycle

Diabetes.
Insulin stimulates testosterone release, testosterone induce insulin resistance, which further increase insulin, leading to type 2 diabetes

The cysts are formed by follicles that failed to mature

Give oral contraceptive, Metformin

Question 7

State lab findings in Ovarian failure

Answer 7

Estrogen Low, LH & FSH High

Question 8

State lab findings in Pituitary failure in women

Answer 8

Estrogen Low, LH & FSH Low

Question 9

What are the two main types of pituitary adenoma? (2)

Answer 9

Prolactinoma & FSH secreting Adenomas

Question 10

State lab findings in Prolactinoma (4)

Answer 10

Prolactin High, Estrogen LH & FSH Low

Question 11

State 3 conditions that can lead to Women hirsutism (3)

Answer 11

PCOS: ovarian-derived testosterone
CAH: 17 OH-progesterone
androgen-secreting adrenal tumor

Question 12

State lab findings in Primary testicular failure (3)

Answer 12

testosterone Low, LH & FSH High

Question 13

State lab findings in hypogonadotropic testicular failure (3)

Answer 13

testosterone Low, LH & FSH Low

Question 14

Suggest a condition leading to GH deficiency in adult. (1) Describe the difference in diagnosing GH deficiency in child & adult. (2) How about acromegaly? (1) Name one additional test that may help diagnosis of acromegaly. (1)

Answer 14

Pituitary failure
Child has low GH, so stimulation test using Insulin & Glucagon is required, lower than expected GH after application of both hormone diagnose GH deficiency in Child.
Suppression test using Glucose is required to diagnose acromegaly as GH is also high when sleeping, exercising, & eating. 1h GH after 100g Glucose intake >1 μg/L indicates acromegaly.

IGF-1, because High GH causes liver to release more IGF-1

Question 15

State 2 primary functions of PTH. (2)
Why Urine Ca is high & Acidosis in patient with high PTH? (2)

Answer 15

Bone resorption increasing plasma Ca
Urine excretion of PHOS decreasing plasma PHOS

Any condition causes high plasma Ca will lead to high urine ca, except in familial hypocalciuric hypercalcemia (FHH), which is CASR mutation leading to increased Ca threshold for PTH secretion & inhibition of Ca reabsorption by kidney.
Acidosis is due to HCO3 loss in urine along with PHOS

Question 16

Explain how ICA & PTH helps classification of Hyper/HypoPTH (4)
Why PTH lab result is normal when PTHRP is high? (1)

Answer 16

HyperPTH 1st: parathyroid gland release PTH, increasing ICA
HyperPTH 2nd: Kidney not responding to PTH, decreasing ICA, parathyroid gland respond by releasing more PTH. In lab finding, PTH increase before ICA decrease.

HypoPTH 1st: parathyroid gland not release PTH, decreasing ICA
HypoPTH 2nd: Cancer cell release PTHRP, increasing ICA, parathyroid gland respond by releasing less PTH.

IMA for PTH should be 2 Ab detecting the N-terminal fragment & intact PTH, PTHRP has the PTH’s N-terminal only so it seldom cross-react in PTH assay.

Question 17

Name 3 hormones from adrenal cortex, 1 hormone from adrenal medulla (4)

Answer 17

Aldosterone, Cortisol, androgen, catecholamines

Question 18

What are the advantage of urine cortisol over plasma cortisol? (3)

Answer 18

Serum cortisol influenced by diurnal variation, cortisol-binding protein & pulse variation
Urine cortisol is excess cortisol after cortisol-binding proteins are saturated, so its level is not fluctuated with those factors.

Question 19

State clinical symptoms of patient with high cortisol or prescribed steroid. (5)

Answer 19

S Stimulant
TE Tarry stool
O Osteoporosis
I Immunocompromised
D DM

Question 20

State 4 conditions of high cortisol (Cushing’s syndrome) & 3 conditions of low cortisol (6)

Answer 20

Glucocorticoid (medication)
ACTH-mediated (2nd): pituitary tumor, also called Cushing disease
non-ACTH-mediated (1st): Adrenal adenoma
Ectopic ACTH: Usually lung cancer, correlate with Placental ALP

Addison’s disease (1st)
Pituitary failure (2nd)
CAH

Question 21

Describe how LDDST, HDDST & ACTH assist in further diagnosis of Cushing’s syndrome. (3)
Suggest two confirmatory tests for Ectopic ACTH. (2)

Answer 21

LDDST is a screening test for Cushing’s syndrome.
1mg dexamethasone given at 11 p.m, cortisol result at 8 a.m. should be <5.0 μg/dL (98%)

HDDST differentiate ACTH-mediated from Ectopic ACTH
8-mg dose of dexamethasone causes 50% cortisol suppression, vs no suppression in Ectopic ACTH

ACTH-mediated: 100~ 200 pg/dL
non-ACTH-mediated: ACTH ~= 0
Ectopic ACTH: ACTH > 200 pg/dL

CRH stimulation test: Absence of ACTH response
Inferior petrosal sinus sampling (IPSS) for MRI negative

Question 22

Explain why synacthen test, ACTH, metyrapone stimulation test & 17 OH-progesterone are useful in further diagnosis of low cortisol. (4)

Answer 22

synacthen test is a screening test for Addison’s disease (1st). Giving 250μg ACTH (synacthen) with no increase of cortisol means Addison’s disease.

Direct measurement of ACTH can also differentiate Addison’s disease (High) from pituitary failure(Low)

metyrapone stimulation test confirms pituitary failure. ACTH remain low after blocked cortisol formation means patient has pituitary failure.

CAH is 11/21/17 hydroxylase deficiency
11/21: high 17 OH-progesterone, ALDO Cortisol Low, Androgen High
17: low 17 OH-progesterone, ADLO High, Cortisol Androgen Low

Question 23

What are Catecholamines? (3)
Why do 24h Urine Catecholamines? (1) suggest another test having the same purpose (1)

Answer 23

Epinephrine, norepinephrine, and dopamine

For screening of Pheochromocytoma
24h Urine of its metabolites, metanephrine & VMA

Question 24

What are the interferences of Catecholamine test? (4)

Answer 24

Elevated in exercise and in muscular diseases
Elevated in drug causing monoamine oxidase inhibition & Epi drug

Question 25

Why we measure pH of urine sample for CAT? (3)

Answer 25

Sample collection with HCL as pH>3 causes degradation pH<2 / >5 cancel, low pH suggest insufficient collection, high pH suggest lack of HCL / bacterial contamination.

Question 26

Why we measure CRE of urine sample for CAT? (2)

Answer 26

urine CRE should be >0.8 g/day to ensure its integrity Report result in μg/mg CRE to correct for renal function

Question 27

Why we measure 5-HIAA? (2) Why sometimes Serotonin is also measured? (1)

Answer 27

For Carcinoid tumors (appendix, lung) Some Carcinoid tumor lack enzyme to convert serotonin to 5-HIAA, measuring 24U serotonin (5-HT) is useful in such case.

Question 28

Why we measure HVA? (2)

Answer 28

For Neuroblastoma +VMA can increase clinical sensitivity to 90%

Question 29

State the TFT pattern of 1st hypothyroidism & 1st hyperthyroidism (2) If TSH & FT4 are rise/fall at same direction, what would you consider? (2) For TFT: TSH Low FT4 Normal, what would you do? (2)

Answer 29

1st hypothyroidism: TSH High FT4 Low 1st hyperthyroidism: TSH Low FT4 High 2nd hypothyroidism (pituitary failure): TSH Low FT4 Low 2nd hyperthyroidism (pituitary tumor): TSH High FT4 High FT3 should be added to differentiate Non-thyroidal conditions (euthyroid sick syndrome) from hyperthyroidism (T3 thyrotoxicosis) In euthyroid sick syndrome, some T4 convert to Reverse T3 instead of FT3, so FT3 should be low.

Question 30

For critically ill patient, TFT should be avoid, why? (3)

Answer 30

Transient pituitary dysfunction in severe illness affects TSH level

Question 31

Why only TSH is ordered for majority of samples? (2)

Answer 31

TSH is very sensitive. It is the earliest marker for thyroid disorder & the slowest marker for effective thyroid treatment

Question 32

Why FT3 is slightly high in iodine deficiency? (1)

Answer 32

DIT production is twice of MIT production normally, but when Iodine is insufficient MIT is favored, so T3 (DIT+MIT) production is increased at the expense of T4 (DIT+DIT).

Question 33

Suggest conditions that can increase and decrease TBG. (5) Do they affect FT4 FT3 measurement? (2)

Answer 33

Increased TBG: Pregnancy & Estrogen (oral contraceptives) Decreased TBG: nephrotic syndrome, cirrhosis, steroid No except steroid, TBG level does not alter levels of free form hormones.

Question 34

Why TSH normal range is slightly lower for pregnant women? (1)

Answer 34

hCG (peaks at first trimester) mimic TSH to stimulate FT4 FT3, TSH become low due to negative feedback. TSH gradually increase as hCG decrease gradually after first trimester

Question 35

Why hsTSH is better than TSH? (3)

Answer 35

TSH<0.03 mU/mL strongly suggest Graves’ disease and rule out non-thyroidal conditions such as hCG, critical illness & steroid.

Question 36

Suggest further tests for Graves’ disease & Hashimoto’s thyroiditis. (3)

Answer 36

Hashimoto’s thyroiditis: Anti-Tg Ab Anti-TPO Ab Anti-TSHR Ab (Blocking type) Graves’ disease: Anti-TSHR Ab (Stimulating type)

Question 37

How to interpret synovial fluid GLU

Answer 37

synovial fluid GLU = plasma GLU - 0.5 -1.4 suggest Inflammatory arthritis -2.2 suggest septic arthritis

Question 38

A patient has high CHO and prescribed statin, it doesn't lower the CHO, what further tests would you recommend? (1)

Answer 38

TFT. Hypothyroidism can cause high CHO. TSH can be normal with low FT4, so a TSH screening is insufficient Thyroid hormone replacement may not decrease CHO in case of receptor problem.