Ovarian Stimulation

Question 1

Why does ovarian stimulation not change the number of follicles a woman begins with in any given cycle?

Answer 1

Primordial follicles making up the cohort are not under gonadotropin control

allows manimulation of the number of follicles that mature and continue growth to point of oocyte maturity

Question 2

How and why do we need to prevent premature LH surge?

Answer 2

GnRH release from the hypothalamus must be regulated to avoid premature surge of LH.

Utilize leuprolide acetate (agonist) or a GnRH antagonist medication

Question 3

What are the common uses for oral medications in Ovarian Stimulation?

Answer 3

Induce ovulation in women with anovulation

induce multifollicular development in women with ovulatory dysfunction or unexplained infertility

induce 1-3 follicles to grow to point of maturity for timed intercourse or IUI

two oral agents used: clomiphene citrate and letrozole

Question 4

What are the two oral agents used for ovarian stimulation?

Answer 4

Clomiphene citrate
Letrozole

Question 5

What is clomiphene citrate?

Answer 5

1. First clinical use in 1967
2. Induce ovulation in 80% of anovulatory women
3. non-steroidal triphenylethylene distnatly related to diethylstilbestrol (selective estrogen receptor modulator SERM)
4. has both estrogen agonist and antagonist properties
5. physiological effect is mostly as pure **estrogen antagonist **unless estrogen levels are low
6. Primary effect at hypothalamus **where occupation and depletion of estrogen receptors **causes an inaccurate interpretation of circulating estrogen levels
7. hypothalamus perceives an artificially low level of estrogen which altrers GnRH secretion
   7. increases the pituitary output of FSH and LH
8. Alteration in gonadal feedback loop on hypothalamus and pituitary to allow multifollicular development

Question 6

What is the typical administration of clomiphene citrate?

Answer 6

5 -day course with 50mg - 150mg
administred cycle days 3-7 or 5-9

racemic mixture of two stereoisomers, enclomiphene (trans-clomiphene) and zuclomiphine (cis-clomiphene)

Enclomiphene is the more potent of the two isomers and is responsible for inducing follicular development. Enclomiphene has a short half-life and is cleared rapidly as opposed to zuclomiphene, which has a longer half-life

The risk for multiple gestations is increased slightly with the use of
clomiphene citrate, with rates reaching 7%-10%

Question 7

What is letrozole and its use?

Answer 7

Letrozole is a triazole (antifungal) derivative, and is a potent, reversible, competitive **inhibitor of aromatase **

Aromatase is a microsomal cytochrome P450 enzyme that catalyzes the rate-limiting step in the production of estrogen, namely, the conversion of androstenedione and testosterone via three hydroxylation steps to estrone and estradiol respectively

blocks the enzyme and thus lowers estrogen production in both the periphery and in the brain at the level of the hypothalamus and pituitary

This results in a compensatory increase in pituitary release of FSH and LH that stimulates follicular growth

After the medication is discontinued and the follicles grow, normal negative feedback by estrogen at the level of the hypothalamus and pituitary will occur because, unlike clomiphene,
letrozole does not deplete the estrogen receptors

Thus, FSH is suppressed and smaller follicles will become atretic and undergo apoptosis.

Question 8

How is letrozole administered?

Answer 8

orally in doses ranging from 2.5-7.5 mg. Similar to clomiphene, a 5-day course on cycle days 3-7 or days 5-9 is typical

Question 9

When were exogenous gonadotropins first used?

Answer 9

1961 with menotropins that provided equivelants of FSH and LH

Question 10

When was recombinant FSH first available?

Answer 10

1996

Question 11

What are human menopausal gonadotropins (hMG)?

Answer 11

Human menopausal gonadotropins (hMG, menotropins) were the only exogenous gonadotropins available for over 30 years

an extract obtained from the urine of postmenopausal women, and a dose contains 75 international units (IU) equivalents of FSH and LH

LH bioactivity actually comes from urinary human chorionic gonadotropin

the modem preparations are purified and can be administered subcutaneously

Question 12

What is urofollitropin?

Answer 12

a derivative of purified urinary FSH

accomplished by removing the LH equivalent utilizing polyclonal anti-hCG antibodies in immunoaffinity columns, taking advantage of the homologous structure of hCG and LH

Subsequent use of FSH specific monoclonal antibodies allowed for greater purity with compounds produced today containing 75 IU of FSH and 0.001 IU of LH equivalent.

Question 13

How was recombinant FSH developed?

Answer 13

came into clinical use in 1996

insertion of the genes encoding the alpha and beta subunits of FSH into the genome of a Chinese hamster ovary cell line. This allows for production of bioactive, dimeric FSH that is purified utilizing immunochromatography and specific anti-FSH monoclonal antibodies

provides batch consistency and production without urinary proteins

more recent use of human retinal cell lines have been studied for more native glycosylation patterns

two recombinant FSH preparations currently available: follitropin alpha and follitropin beta

Question 14

What are follitropin alpha and beta and how are they different?

Answer 14

Two recombinant FSH preparations are currently available, follitropin alpha and follitropin beta. Both are structurally identical to native FSH but differ in their post translational glycosylation process and procedures related to their purification. The biological activity of the two is identical.

Question 15

Is recombinant LH available and is it useful?

Answer 15

Recombinant human LH that has the same bioactivity of pituitary LH is available in 75 IU doses.

Given its short half-life, recombinant LH is not commonly used. Rather, formulations of hCG, which have similar structure to LH and similar bioactivity at the level of the ovary, are used preferentially.

Question 16

what is corifollitropin alpha, and its benefits and uses?

Answer 16

Additional genetic engineering has made a long-acting form of FSH available.

This involved a chimeric gene coding sequences of the FSH beta-subunit and the C-terminal peptide of the hCG beta-subunit. This portion of the hCG subunit contains glycosylation sites, which accounts for hCG’s long half-life.

This attribute is conferred on this new recombinant FSH formulation, termed corifollitropin alpha. Corifollitropin alpha has a** half-life of 95 hours**, as opposed to recombinant FSH, which has a half-life of 32 hours

Thus, a single dose of 100 micrograms can sustain multi-follicular growth for a week in women undergoing ovarian stimulation during IVF

It is not optimal in patients undergoing superovulation in conjunction with intercourse or IUI as there is a lack of control, which results in too many follicles being recruited.

Question 17

Why is premature ovulation an issue during ovarian stimulation?

Answer 17

When a patient undergoes ovarian stimulation, the estradiol levels far surpass the estradiol threshold that
would cause an LH surge under physiologic conditions

Question 18

What are the physiological effects of taking GnRH agonists?

Answer 18

GnRH agonists initially stimulate LH and FSH release, however with prolonged use it will suppress gonadotropins due to downregulation of GnRH receptors at the level of the pituitary

Once suppression has occurred, the ovaries can be stimulated with exogenous gonadotropins

Question 19

What is the most common GnRH agonist and dosage?

Answer 19

The most common GnRH agonist is leuprolide acetate, given subcutaneously at doses of 0.25-1.0 mg/day

An alternative use of leuprolide is the microdose leuprolide protocol during which a smaller dose of the GnRH agonist leuprolide acetate is given (40-50 µg twice daily).

Question 20

What are GnRH antagonists and their advanatages?

Answer 20

GnRH antagonists are a more recent development in ovulation prevention. Their main advantage is that they directly antagonize the GnRH receptors at the level of the pituitary and have an immediate effect. The usual dose is 250 µg/day

Question 21

What is medroxyprogesterone and its applications?

Answer 21

The most recent development in **ovulation prevention **is the use of medroxyprogesterone acetate (MPA). The use of this medication must be done in conjunction with a freeze of all the embryos and a subsequent frozen embryo transfer, as the progesterone has an effect on the endometrial lining causing the onset of luteal transformation and making an embryo transfer in the cycle that the oocytes are retrieved impossible

Studies to date have been promising, showing no difference in oocyte and embryo yield and no difference in pregnancy rates in subsequent frozen embryo transfers

Question 22

When and why is DHEA supplementation used?

Answer 22

In women who have ovarian insufficiency, some degree of androgen insufficiency may exist when compared to women without ovarian insufficiency. Indeed, some data exist that ovarian androgens (androstenedione and/or testosterone) were lower in age matched women with ovarian insufficiency (23). These data lead to DHEA supplementation for women with low ovarian reserve or poor oocyte quality

Overall, 50-75 mg of DHEA supplementation for at least 4 months may result in improved outcomes for natural cycle IVF in women with diminished ovarian reserve, premature ovarian failure or premature ovarian aging. Improved outcomes in terms of oocyte and embryo quality have been reported (24), although these benefits are modest

Question 23

Why is GH supplementation used?

Answer 23

The physiologic basis for supplementing IVF cycles with GH comes from the oocyte­ granulosa cell crosstalk involving a number of growth differentiating factors stimulated by GH, in particular insulin-like growth factors 1 (IGF-1) and 2 (IGF-2). Several animal models show increased follicular IGF-1 and IGF-2 as well as oocyte competence

A series of meta-analyses have shown that, although GH supplementation did not increase controlled ovarian stimulation response or number of oocytes, both pregnancy rates and live-birth rates did increase, perhaps speaking to oocyte quality

At present, there is not a standard dose, ranging from 4IU to 24IU, nor standard duration of treatment, ranging from initiation in the prior cycle to day 8 of ovarian stimulation

Question 24

What are the symptoms of ovarian hyperstimulation syndrome?

Answer 24

OHSS refers to a spectrum of findings that include ovarian enlargement due to multifollicular development and acute shift of fluid out of the intravascular space

The most severe forms can include severe third-space accumulation of fluid and hemoconcentration, which can result in renal failure, acute respiratory distress syndrome, thromboembolic disease, hypovolemic shock, and death

This disease process is nearly unique to pharmacologic manipulation of the hypothalamic-pituitary-ovarian access, as feedback mechanisms prohibit excessive stimulation from occurring in the natural state aside from rare case reports in patients with PCOS or FSH receptor mutations

Question 25

What is the pathophysiology of OHSS?

Answer 25

The underlying pathophysiology is luteinization of large numbers of follicles. Typical onset is 5-10 days after the ovulatory trigger, either hCG or GnRH agonist. One of the major factors appears to be vascular endothelial growth factor (VEGF), which is thought to be causal in the capillary permeability. VEGF is a potent promoter of neovasculogenesis and vascular permeability, mediated in part by nitric oxide

Question 26

How can OHSS incidence or severity be reduced?

Answer 26

The two most common include coasting, where the trigger medication is delayed until the estradiol falls to a more acceptable range (typically less than 2,500 to 3,000 pg/mL) and substituting an hCG ovulation trigger, which has a long half-life, with a GnRH agonist trigger

The latter can only be done in a patient who has a functional hypothalamic-pituitary-gonadal axis at the outset and one that has not been down-regulated as part of the IVF cycle regimen.

, the best treatment is prevention. This can be accomplished in most cases by choosing the appropriate starting dose of gonadotropins taking into account the patient’s age, basal antral follicle count, serum ovarian reserve testing, and any information about prior response to gonadotropins. Furthermore, careful monitoring of follicular growth and estradiol level will allow for appropriate decrease, or “step down,” in the dose of gonadotropins when there is an exaggerated ovarian response

In women who develop OHSS, close observation with frequent monitoring for hemoconcentration, hydration status, and electrolyte disturbances is required. The patient may require intravenous fluid to rehydrate and/or correct metabolic disturbances, anticoagulant therapy if the risk of thromboembolism is high, and removal of excessive fluid from the third-spaces, such as the abdomen and the lungs

Question 27

How does ovarian stimulation alter or impaire endometrial receptivity?

Answer 27

In addition to ovarian stimulation affecting the endometrium, there is also good evidence to show that stimulation can lead to a premature rise in progesterone that impacts embryo-endometrial synchrony

Monitoring for progesterone rise at the end of the follicular phase has shown that an increased level of progesterone prior to ovulation trigger impacts endometrial receptivity (31). Recognition of the premature rise in progesterone may allow for intervention and improvement of outcomes when synchrony is actively managed

Question 28

What is minimal stimulation?

Answer 28

Some of the quoted advantages include decreased risks of OHSS and multiple gestation (although this factor is still dependent upon transfer order, ultimately), and no need for frozen embryo storage

Despite these advantages, standard IVF has the advantage of a higher likelihood of live birth per cycle.