Sex Hormones & Menstrual Cycle

• The text contains information on sex hormones, birth control pills, and the menstrual cycle
• It describes what hormones do in both men and women, and where they are created

Sex Hormones

• The hypothalamus in the brain produces GnRH, signaling the pituitary gland for the release of LH and FSH
• In men, the primary sex hormones are testosterone, LH (luteinizing hormone), and FSH (follicle-stimulating hormone)

Testosterone

• Primarily produced in the testicles, with small amounts in the adrenal glands
• Responsible for developing male characteristics such as male sex organs, a deeper voice, facial hair, and muscle mass

LH (Luteinizing Hormone) and FSH (Follicle-Stimulating Hormone)

• LH stimulates Leydig cells in the testicles to produce testosterone
• FSH helps stimulate Sertoli cells, aiding sperm production

Regulation of Sex Hormones

• High testosterone levels inhibit GnRH and LH production, creating a negative feedback loop

Egg Release and Menstruation

• Follicles mature in the ovaries each month, each containing an egg cell
• Usually, only one follicle becomes dominant
• FSH (follicle-stimulating hormone), produced in the pituitary gland, governs egg maturation
• LH (luteinizing hormone) triggers ovulation when the egg is mature, releasing the egg from the follicle into the fallopian tube

Egg Fertilization

• An egg moves through the fallopian tube toward the uterus, where it can be fertilized
• If the egg isn't fertilized, it dissolves, hormonal levels fall, and the uterine lining sheds, causing menstruation
• The menstrual cycle repeats unless the egg is fertilized and implants in the uterus, leading to pregnancy
• The cycle lasts about 28 days and has four phases:

Growth Phase

• A primary follicle matures in the ovary, and estrogen increases, thickening the uterine lining

Ovulation

• A mature follicle ruptures releasing the egg
• Estrogen levels are high, and the endometrium is thin and meant for fertilization

Secretory Phase

• The corpus luteum develops in the ovary, producing progesterone and estrogen
• The uterine lining thickens and becomes sticky to avoid bacteria

Menstruation

• If the egg is not fertilized, decreased progesterone and estrogen levels cause the shedding of the uterine lining

Birth Control Pills

• Synthetic forms of estrogen and progesterone, mimicking natural hormones to prevent ovulation
• They elevate hormone levels in the body, impacting the hypothalamus and pituitary gland through a negative feedback mechanism
• Reduces FSH and LH production, inhibits ovulation and prevents pregnancy

Additional Information

• FSH controls egg maturation
• LH is the hormone that controls ovulation

Follicles

• Assist the egg in maturing

Corpus Luteum

• Formed from where the egg separated in the eggstock
• It produces the female sex hormones estrogen and progesterone

Male and Female Primary Sex Hormones

• Estrogens
• Progestogens
• Androgens

Estrogens

• Produced mainly in the ovaries by the follicles, smaller amounts are also produced in the adrenal glands and fat
• Functions include: building female characteristics, controls menstruation
• Stimulates the growth of the endometrium before egg release
• Ensures bones stay strong and skin stays elastic

Progesterone

• Made in the corpus luteum in the ovaries after the egg is released and in the placenta during pregnancy
• Its job is to strengthen the endometrium for possible pregnancy, reduce uterus squeezes to avoid early delivery, and hold back the production of new follicles during pregnancy

Testosterone in Females

• Produced in small amounts in the ovaries and adrenal glands
• Functions include: contributes to libido (sex drive) and affects muscle mass and bone strength

Testosterone in Males

• Produced mainly in the Leydig cells of the testicles, with smaller amounts in the adrenal glands
• Functions include: creates male characteristics, boosts sperm production, boosts libido and aggressive behavior, ensures strong bones and muscle building

Estrogen in Males

• Produced in small amounts in the testicles and fatty tissues
• Function: controls sperm cell production and ensures the bones and heart stay healthy

Menstrual Cycle

• Menstrual cycle lasts about 28 days on average, but can vary from 21 to 35 days
• There are three phases:

Follicular Phase

• During days 1-14
• The pituitary gland puts out FSH to boost follicle maturation in the ovaries
• This also boosts estrogen production
• The follicles make estrogen, which builds up the endometrium, with LH peaking around day 14 to set off egg release

Egg Release (Day 14)

• A ripe follicle breaks open and releases an egg, estrogen levels dip briefly when LH peaks

Luteal Phase (Days 15-28)

• The burst follicle turns into the corpus luteum, which produces progesterone
• If the egg is not fertilized, progesterone levels drop, and the endometrium is shed through menstruation

P-Pills and Hormones

• Birth control pills use artificial forms of estrogen and progesterone to:
• Prevent ovulation
• Thicken the cervical mucus to block sperm
• Thin the uterine lining to prevent implantation of a fertilized egg

Types of P-Pills

• Combination pills: contain both estrogen and progestin
• Mini-pills: only contain progestin and are often used by women who cannot tolerate estrogen