Hormones - hCG Flashcards
Source
Syncytiotrophoblast
Memory aid:
- h_C_G
- syn_C_ytiotrophoblast
When detected? What is the implication?
- When tested
- 8 to 9 days after ovulation (in maternal serum or urine)
- 6–12 days after fertilization (3–3.5 weeks after the LMP)
- in maternal serum after implantation has taken place, ≈ 8–11 days after conception
- Implication
- Do not assay for hCG before a woman has missed a menstrual period because of low test sensitivity before this time
Level
- Peak
- Plateau
- Peak
- 8 - 10 weeks
- Plateau
- 16 weeks
Composition and origin
Glycoprotein (of two subunits—α and β) made by syncytiotrophoblast
What subunit is the same with other hormone? What is the implication?
- The α subunit
- The β subunits are unique: Urine and serum tests are based on antibody specificity to β subunit of hCG
Memory aid: S_α_me
The α-subunit is similar to what hormones?
- Luteinizing hormone (LH)
- Follicle-stimulating hormone (FSH)
- Thyroid-stimulating hormone (TSH)
- Memory aid:*
- FLαT
Function of hCG
Helps sustain the corpus luteum during the first 7 weeks; after the first 7 weeks, the placenta makes its own hormones to sustain the pregnancy
Rate of hCG increase
in general, hCG should double every two days prior to 10 weeks
What if β-hCG does not rise as expected?
Consider accidents of pregnancy: spontaneous abortion, missed abortion, ectopic pregnancy
Other conditions that produce hCG
- Hydatidiform mole
- Choriocarcinoma
- Germ cell tumors
- Breast cancers and large cell carcinoma of the lung
In relation to hCG, when can gestational sac be visualized with TVS?
When hCG levels are > 1500
What if the hCG is >1500 and no evidence of intrauterine pregnancy
Think ectopic pregnancy
Urine hCG
- Best time of collection
- Level detectable by assay
- Best time of collection
- First morning specimens are more accurate
- hCG concentration is higher in the morning
- First morning specimens are more accurate
- Level detectable by assay
- 12.5 mU/mL
