Lab Testing for Endocrine and Repro Disorders (Krasowski)

Question 1

part of the glycoprotein hormone family that includes LH, FSH and TSH, but has a longer half life becuase of heavy glycosylation

Answer 1

hCG

Question 2

hCG has considerable molecular heterogeneity with different isoforms such as _____ hCG and ____ hCG - these variants mostly are an issue with hCG-producing neoplasms

Answer 2

hyperglycosylated; “nicked”

Question 3

A highly specific, two-antibody test for hCG is known as what?

Answer 3

sandwhich immunoassay

Question 4

All of the following are conditions that elevate hCG EXCEPT:

A. Pregnancy and menopause
B. Gestational trophoblastic tumors
C. Pituitary tumors
D. Germ cell tumors
E. Teratomas

Answer 4

C

Question 5

discrepancies between hCG pregnancy tests and hCG tumor marker tests suggest what?

Answer 5

a neoplasm

Question 6

39 year old female is in pre-operative suite prior to elective surgery. Per hospital protocol, she is tested for pregnancy before starting the surgery. Her last pregnancy was five years ago and resulted in a healthy, full-term girl.
Urine pregnancy testing is positive even though the patient is very surprised by the results given that her husband had a vasectomy six months ago and she has not been sexually active with anyone else. However, the patient is told she is pregnant and the surgery is cancelled.
After the “unexpected” positive pregnancy test, what would have been the most appropriate next step?

A. No change from what occurred

B. Perform trans-vaginal ultrasound

C. Perform a quantitative serum hCG test

D. Proceed with elective surgery

Answer 6

C. This will be very informative and guide next steps with less invasion than a transvaginal ultrasound.

Question 7

What is the MOST LIKELY cause of the “unexpected” urine pregnancy result in the previous case?

A. Cervical cancer

B. Endometrial cancer

C. Menopause

D. Gestational trophoblastic neoplasia

E. Specimen mix-up

Answer 7

E. The others are unlikely and gestational trophoblastic neoplasia typically occurs more closely following normal or abnormal pregnancy.

Question 8

what is the main benefit and main drawback of immunoassay as the primary hormone testing method?

Answer 8

benefit: it is fast and inexpensive
drawback: cross-reactivity with related compounds

Question 9

what 3 hormones occasionally present with issues regarding cross-reactivity on immunoassays?

Answer 9

cortisol, insulin and testosterone

Question 10

when might you use mass spectrometry over immunoassay?

Answer 10

1. when the compound does not have an immunoassay avaiable (ie 17-OH-progesterone)
2. when cross-reactivity is an issue (ie, cortisol, insulin or testosterone)
3. when measuring very low levels of testosterone or estradiol

Question 11

18 year old women treated with prednisone for severe asthma has elevated cortisol and suppressed ACTH. Is the elevated cortisol due to prednisone cross-reactivity with the cortisol assay or is the patient actually producing cortisol endogenously?

Answer 11

Answer: Prednisone likely cross-reacts with the cortisol immunoassay. The suppressed ACTH would be consistent with prednisone therapy.

Question 12

22 year old male presents to primary care clinic for concern about difficulty maintaining erections during sexual intercourse and is concerned he has “low T”. He is very muscular and has extensive acne over his face. Physical examination shows testicular atrophy. A serum testosterone concentration is at the top end of the reference range. Does this rule out “low T”?

Answer 12

Case is suspicious for abuse of anabolic steroids (very muscular, testicular atrophy, gynecomastia, acne). Some of these (e.g., methyltestosterone) cross-react with testosterone immunoassays.