Contraception

What axis menstrual cycle controlled by?

Hypothalamic-pituitary-gonadal (HPG) Axis

What does the hypothalamus secrete and in what pattern?

secretes gonadotropin-releasing hormone (GnRH) in a pulsatile fashion

Abbreviation for gonadotropin-releasing hormone?

GnRH

what does GnRH stimulate? and what is released as a result?

anterior pituitary releases luteinizing hormone (LH) and follicle-stimulating hormone (FSH).

What do LH and FSH control the production of in the ovaries?

Estrogens and progestogens

What do follicles contain?

fluid and ovum (egg)

what step of meiosis is egg frozen in?

First Step

Gonadotropins stimulate the maturation and growth of how many ovarian follicles?

several but typically only 1 dominant follicle matures to contain the egg

When the dominant follicle ruptures where is the ovum released?

Into the peritoneal cavity

After ovulation what do the remaining follicular cells become?

Corpus Luteum (it makes hormones to prepare body for pregnancy)

What feedback mechanism regulates the HPG axis?

Both positive and negative feedback

What happens during menstruation (days 1-5)?

Endometrial shedding due to corpus luteum regression → ↓estrogen/progesterone.

Why do FSH and LH rise during menstruation?

Loss of negative feedback from estrogen/progesterone

What characterises the follicular/proliferative phase (days 4-14)?

Follicle maturation

What triggers ovulation (around day 14)?

LH surge caused by sustained high estrogen levels. (The high estrogen levels cause a brief positive feedback effect on LH and FSH causing the mid-cycle surge)

What is formed after ovulation from the follicle?

The corpus luteum

What does the corpus luteum secrete?

Estrogen + progesterone (progesterone is dominant)

What does progesterone do in the luteal/secretory phase?

Prepares endometrium for implantation

What hormone maintains the corpus luteum if pregnancy occurs?

hCG from the blastocyst (human chorionic gonadotropin)

What produces progesterone after 10-12 weeks of pregnancy?

The placenta

What are the two main types of hormonal contraception?

Combined (estrogen + progestin) and progestin-only.

Why is estrogen always combined with progestin in women with a uterus?

To prevent endometrial hyperplasia and cancer from unopposed estrogen

Examples of synthetic estrogens?

Ethinylestradiol

Examples of synthetic progestins?

Levonorgestrel

MoA of combined hormonal contraception?

Dual negative feedback → suppresses GnRH

What are monophasic vs multiphasic formulations?

Monophasic: constant hormone dose for 21 days + 7 placebo (withdrawal bleeding). Multiphasic: varying doses to mimic natural cycle.

Non-contraceptive benefits of combined contraceptives?

Reduced menstrual symptoms

Common adverse effects of combined hormonal contraception?

Weight gain

Serious risks of combined hormonal contraception?

DVT

How does progestin-only contraception work?

Thickens cervical mucus

What formulations are available for progestin-only?

Mini-pill (daily)

Which contraceptives are most effective?

Long-acting reversible contraceptives (implants

Advantage of progestin-only over combined?

No thrombotic risk.

What is emergency contraception and how does it work?

High-dose progestin or SPRM; prevents/delays ovulation

Examples of emergency contraceptives?

Levonorgestrel (within 72h)

What is ulipristal's mechanism?

Selective progesterone receptor modulator (SPRM) with antagonist/partial agonist activity.

Why may ulipristal be less effective with other progestins?

Receptor competition.

How are hormonal contraceptives metabolised?

By CYP3A4 in the liver.

Which drugs reduce their effectiveness?

CYP3A4 inducers (phenytoin