564 Obstetrics and Gynecology Board Review •••
❍ When is maximal response usually noted?
By 3 months.
❍ How long does it typically take for menses to return after cessation of GnRH agonist treatment?
4 to 10 weeks.
❍ How long does it typically take for myoma and uterine size to return to pretreatment levels after cessation of
GnRH agonist treatment?
3 to 4 months.
❍ Why might a GnRH agonist be useful in the treatment of hyperandrogenism?
The assumption is that the hyperandrogenism is at least in part gonadotropin-dependent, and that long-term
treatment with GnRH agonists will inhibit LH and to a lesser extent FSH leading to a decline in ovarian function
and consequently ovarian androgen production.
❍ Why is GnRH agonist therapy not the recommended first-line treatment of ovarian hyperandrogenism?
GnRH agonist therapy should be considered only after failure of OCP therapy with or without spironolactone, because
GnRH agonist treatment causes severe hypoestrogenism, and add-back therapy is necessary if treatment is continued
for more than a few months. Also, agonist is expensive compared with OCPs, and must be given parenterally.
❍ Does the GnRH agonist therapy decrease adrenal androgen secretion?
No.
❍ What are the pros and cons of evoking a midcycle LH surge using GnRH agonists?
Decreased probability of ovarian hyperstimulation is a possible benefit. It is still not certain whether corpus luteum
function following ovulation induction by GnRH agonists is adequate to sustain nidation and continuation of
pregnancy or if pharmacological luteal support is mandatory.
❍ What percentage of bone loss occurs in women on GnRH therapy for 6 months?
5% to 10%.
❍ How are the GnRH antagonists synthesized?
With multiple amino acid substitutions that allow binding of the antagonist to GnRH receptor and competitive
inhibition.
❍ How long does it take to produce suppression by GnRH antagonists?
It is an immediate action resulting in therapeutic effects within 24 to 72 hours.
❍ Why is response to antagonist treatment faster than to agonist?
Because there is no initial flare response.
❍ What are the treatment indications of use of GnRH antagonists?
Endometriosis, prostate cancer, precocious puberty, and female infertility.