A 28-year-old woman on combined oral contraceptive (COC) therapy presents with amenorrhea for 3 months. Her pregnancy test is negative. Regarding the mechanisms and clinical effects of progestins in COCs, all of the following are true EXCEPT:

Question

Accepted Answer

B. Progestins enhance myometrial contractility and promote uterine peristalsis to facilitate sperm transport. ## Progestin Mechanisms in Contraceptive Use

### Correct Statements (Options 0, 1, 3)

**Option 0 — Endometrial atrophy and amenorrhea:**

**Key Point:** High-dose or prolonged progestin exposure suppresses endometrial proliferation and causes endometrial atrophy. This is the mechanism behind amenorrhea or hypomenorrhea in some COC users. The endometrium becomes thin and inactive, unable to support normal menstrual bleeding.

**Option 1 — Basal body temperature elevation:**

**High-Yield:** Progestins increase basal body temperature (BBT) by 0.5–1°C by acting on the hypothalamic thermoregulatory center (preoptic area). This is a well-documented effect and is used in fertility awareness methods. The mechanism involves altered sensitivity to norepinephrine in the hypothalamus.

**Clinical Pearl:** This BBT rise occurs in the luteal phase naturally and is mimicked by exogenous progestins, making it a reliable marker of ovulation or progestin exposure.

**Option 3 — Estrogen receptor antagonism:**

**Key Point:** Progestins downregulate estrogen receptors (ER-α and ER-β) in the endometrium and other target tissues. This antagonizes estrogen-induced proliferation and is a fundamental mechanism of progestin action. This is why progestins are used in hormone replacement therapy (HRT) to protect the endometrium from unopposed estrogen stimulation.

### Incorrect Statement (Option 2) — THE ANSWER

**Warning:** This statement contains a critical mechanistic error. Progestins **DECREASE myometrial contractility**, not increase it.

**Mechanism of progestin action on myometrium:**
1. Progestins reduce the frequency and amplitude of uterine contractions
2. They decrease gap junction formation (connexin-43) between myometrial cells
3. They reduce myometrial responsiveness to oxytocin
4. This creates a **quiescent uterus** suitable for pregnancy maintenance

**Sperm transport:** Sperm transport to the fallopian tubes is facilitated by **estrogen-induced uterine contractions**, not progestin-induced contractions. Progestins actually **impair sperm transport** by reducing myometrial peristalsis, which is another contraceptive mechanism (in addition to cervical mucus thickening).

### Mnemonic: Progestin Effects

**"DREAM"**
- **D** = Downregulates estrogen receptors
- **R** = Raises basal body temperature
- **E** = Endometrial atrophy (high dose)
- **A** = Antagonizes myometrial activity (reduces contractions)
- **M** = Mucus thickening (cervical)

| Effect | Mechanism | Clinical Relevance |
|--------|-----------|-------------------|
| Endometrial atrophy | Suppresses proliferation | Amenorrhea, hypomenorrhea |
| BBT elevation | Hypothalamic action | Marker of ovulation/progestin effect |
| ER downregulation | Receptor antagonism | Protects endometrium from estrogen |
| **Myometrial quiescence** | **Reduces contractions** | **Impairs sperm transport; maintains pregnancy** |

Answer

A. Progestins increase basal body temperature by acting on the hypothalamic thermoregulatory center

Answer

C. High-dose progestins can suppress endometrial proliferation and cause endometrial atrophy, leading to amenorrhea or hypomenorrhea

Answer

D. Progestins antagonize estrogen-induced endometrial proliferation by downregulating estrogen receptors in the endometrium

A 28-year-old woman on combined oral contraceptive (COC) therapy presents with amenorrhea for 3 months. Her pregnancy test is negative. Regarding the mechanisms and clinical effects of progestins in COCs, all of the following are true EXCEPT:

Explanation

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