A 32-year-old woman with secondary infertility (1 year of unprotected intercourse) and anovulation is being considered for ovulation induction. Her BMI is 24 kg/m², baseline FSH is 6 mIU/mL, and transvaginal ultrasound shows normal ovaries without polycystic morphology. Which is the most common first-line agent used for ovulation induction in this patient?

Explanation

## First-Line Agent for Ovulation Induction: Clomiphene Citrate **Key Point:** Clomiphene citrate (CC) is the most common and first-line agent for ovulation induction in women with anovulation, normal BMI, and normal baseline FSH levels. It is a selective estrogen receptor modulator (SERM) that acts as an estrogen antagonist at the hypothalamic-pituitary level. ### Mechanism of Action 1. **Competitive antagonism** of estrogen at hypothalamic and pituitary estrogen receptors 2. **Increased GnRH secretion** from the hypothalamus 3. **Increased FSH and LH secretion** from the anterior pituitary 4. **Follicular recruitment and development** in the ovary 5. **Ovulation** (if adequate estrogen feedback is maintained) ### Indications for Clomiphene Citrate - **Anovulation** (PCOS, hypothalamic amenorrhea, idiopathic anovulation) - **Normal or low-normal FSH** (indicates intact hypothalamic-pituitary-ovarian axis) - **Normal BMI** (obesity reduces CC efficacy) - **Unexplained infertility** with anovulation - **Luteal phase defect** (with luteal support) ### Dosing and Protocol | Parameter | Standard Protocol | | --- | --- | | Starting dose | 50 mg daily for 5 days | | Timing | Days 3–7 or 5–9 of cycle | | Escalation | Increase by 50 mg increments if no ovulation | | Maximum dose | 150–200 mg daily | | Ovulation rate | 70–80% in anovulatory women | | Pregnancy rate | 30–40% per cycle (cumulative 60–70% over 6 cycles) | **Clinical Pearl:** Ovulation typically occurs 5–10 days after the last dose of clomiphene. Intercourse should be timed around expected ovulation (confirmed by LH surge, BBT rise, or transvaginal ultrasound). ### Advantages of Clomiphene Citrate 1. **Oral administration** — non-invasive, patient-friendly 2. **Cost-effective** — inexpensive compared to gonadotropins 3. **Minimal monitoring required** — fewer ultrasound visits than gonadotropins 4. **Low risk of OHSS** — mild ovarian stimulation 5. **Established safety profile** — decades of clinical use ### Side Effects **Common:** - Hot flushes (10%) - Mood swings, depression - Visual disturbances (blurred vision, floaters) — reversible, dose-dependent - Abdominal bloating **Rare but serious:** - Ovarian hyperstimulation syndrome (OHSS) — <1% with CC - Ovarian cysts - Thromboembolic events (very rare) **Warning:** Visual symptoms warrant immediate cessation and ophthalmologic evaluation. CC should not be used for >6 cycles due to increased risk of ovarian cancer (controversial, but standard practice). ### Failure and Escalation **Clomiphene-resistant anovulation** (10–15% of patients): - Increase dose to 150–200 mg daily - Add metformin (if PCOS) - Add dexamethasone (if adrenal hyperandrogenism) - Switch to **gonadotropins** or **letrozole** if no response after 6 cycles **Mnemonic: CC Indications — "CLOM"** - **C**ost-effective, oral agent - **L**ow-risk OHSS - **O**vulation induction in anovulation - **M**inimal monitoring needed ## Why Other Options Are Not First-Line **Letrozole** (aromatase inhibitor): - Second-line agent, increasingly used as alternative to CC - Better ovulation rates in PCOS, fewer side effects - Not first-line in general anovulation without PCOS - More expensive than CC **Gonadotropins (FSH/hCG)**: - Reserved for CC-resistant anovulation or IVF cycles - Requires intensive monitoring (frequent ultrasounds) - Higher cost - Higher OHSS risk - First-line only in hypogonadotropic hypogonadism (low FSH + low LH) **GnRH agonist**: - Used for pituitary downregulation in IVF, not for ovulation induction monotherapy - Causes initial FSH/LH surge followed by suppression - Not appropriate as first-line agent in this scenario [cite:ASRM Guideline on Ovulation Induction 2013; Speroff & Fritz Clinical Gynecologic Endocrinology 8e Ch 30]