RHSHGU 2 Hormonal Contraception

🩸 PHRM 312 — Hormonal Contraception

FULL TEACHING (Learning Objectives → Cases)

🧠 LEARNING OBJECTIVE 1

Articulate the effects of hormonal contraceptives on the natural menstrual cycle
1⃣ First: the NORMAL menstrual cycle (baseline)

Think of the cycle as brain → ovary → uterus:

  • Hypothalamus releases GnRH (pulsatile)

  • Pituitary releases FSH & LH

  • Ovary

    • FSH → follicle development → estrogen

    • LH surge → ovulation

  • After ovulation

    • Corpus luteum → progesterone

  • If no pregnancy

    • Estrogen & progesterone fall → menstruation

Key idea:
➡ Ovulation only happens if LH surges.

2⃣ What hormonal contraceptives do instead

Hormonal contraceptives override this entire system.

Combined hormonal contraceptives (CHC: estrogen + progestin):

  • Create constant hormone levels

  • Brain thinks: “Oh, we’re pregnant”

  • Result: no GnRH → no FSH/LH → no ovulation

This is why the slide says CHCs:

“abolish the normal menstrual cycle with an artificial cycle mimicking pregnancy”

3⃣ Three core mechanisms (HIGH YIELD)

All hormonal contraceptives rely on some combo of these:

✅ 1. Prevent ovulation

  • Estrogen suppresses FSH

  • Progestin suppresses LH

  • No LH = no ovulation

✅ 2. Thin the endometrium

  • Progestins make the uterine lining:

    • thin

    • underdeveloped

    • less vascular

  • Poor environment for implantation

✅ 3. Thicken cervical mucus

  • Thick, sticky mucus

  • Sperm can’t get through

📌 Progestin does all 3
📌 Estrogen mainly stabilizes bleeding + cycle control

4⃣ What is the “period” on birth control?

IMPORTANT:

  • It is NOT a true period

  • It is a withdrawal bleed

  • Caused by hormone-free interval

This is why:

  • You don’t need to bleed

  • Continuous dosing is safe

  • Amenorrhea ≠ unhealthy

🧠 LEARNING OBJECTIVE 2

Explain MOA, dosing, effectiveness, benefits & risks of hormonal methods

🧪 TYPES OF HORMONAL CONTRACEPTIVES

Tiered by effectiveness (EXAM FAVOURITE)
🔝 Tier 1 — LARC

<1 pregnancy / 100 women per year

  • IUDs (hormonal, copper)

  • Implant

🔸 Tier 2 — SARC

4–7 pregnancies / 100 women

  • Pills

  • Patch

  • Ring

  • Injection

🔻 Tier 3

>13 pregnancies / 100 women

  • Condoms alone

  • No hormones

💊 COMBINED HORMONAL CONTRACEPTION (CHC)

Includes:

  • Pills

  • Patch

  • Ring

Effectiveness:

  • Perfect use: 0.1–0.3%

  • Typical use: ~9%

Estrogen dose (VERY high yield)

  • Old pills: up to 150 mcg

  • Modern standard: ≤35 mcg ethinyl estradiol

Why lower estrogen?

  • ↓ nausea, bloating, breast tenderness

  • ↓ VTE, stroke, MI risk

📌 Higher estrogen = higher clot risk

Progestins (know the themes, not memorization)

Generation

Key idea

1st–2nd

More androgenic

3rd

Less androgenic, slightly ↑ VTE

4th (drospirenone)

Anti-androgenic, anti-mineralocorticoid

📌 Drospirenone:

  • Less acne/hirsutism

  • Slightly ↑ VTE risk

  • Risk of hyperkalemia

CHC risks (absolute numbers matter)
VTE risk per year:

  • No hormones, not pregnant: 2/10,000

  • CHC: 5–12/10,000

  • Pregnancy: 17/10,000

📌 CHC risk < pregnancy risk

Cancer effects (VERY testable)

Cancer

Effect

Breast

Slight ↑ during use, gone after 10 yrs

Cervical

↑ with long use

Endometrial

↓ risk (~30%)

Ovarian

↓ risk (30–50%)

Colorectal

↓ risk

🚫 CHC CONTRAINDICATIONS (MEMORIZE THESE)

ABSOLUTE 🚨:

  • Migraine with aura

  • History of VTE/PE

  • Smoker >35 years (>15 cig/day)

  • Breast cancer

  • Uncontrolled HTN

  • Ischemic heart disease

  • <6 weeks postpartum breastfeeding

Mnemonic: CHC = Clots & Headaches

💊 PROGESTIN-ONLY CONTRACEPTION

Includes:

  • POPs

  • Injection (DMPA)

  • Implant

  • Hormonal IUD

Why we love them:

  • No estrogen → much safer

  • Can be used in:

    • Migraine with aura

    • Smokers >35

    • VTE history

    • Breastfeeding

POP differences (exam detail)

Feature

Norethindrone

Drospirenone

Ovulation suppression

~40%

Consistent

Timing window

3 hours

24 hours

Schedule

Continuous

24/4

DMPA (injection)

Pros:

  • Good for adherence issues

  • Breastfeeding-safe

  • Bypass first pass metabolism (seizure meds okay)

Cons:

  • Weight gain

  • Bone loss

  • Delayed return to fertility (10–18 months)

🧠 LEARNING OBJECTIVE 3

Choosing the right method for the patient

This is pattern recognition.

Think in this order:

  1. Estrogen allowed or NO?

  2. Adherence issues?

  3. Drug interactions?

  4. Patient preferences?

🧠 LEARNING OBJECTIVE 4

Counseling & adherence

HIGH-YIELD counseling points:

  • Backup x 7 days when starting late

  • ACHES for CHC

  • BTB common in first 3 months

  • Missed pills matter MOST in week 1

🧠 LEARNING OBJECTIVE 5

Risk–benefit & referral

Refer when:

  • Migraine with aura + estrogen request

  • Unexplained bleeding

  • Suspected VTE symptoms

  • Breast cancer history