The hormonal control of sperm production in males and of the menstrual cycle in females, including the roles of the pituitary hormones FSH and LH and the gonadal hormones testosterone, oestrogen and progesterone, and the negative and positive feedback that regulates them.

What this dot point is asking

The SQA wants you to explain how FSH, LH and testosterone control sperm production by negative feedback, describe the hormonal control of the menstrual cycle through the follicular and luteal phases, explain the roles of FSH, LH, oestrogen and progesterone, and explain the positive feedback that triggers ovulation.

Hormonal control of sperm production

In the male, two pituitary hormones and one gonadal hormone work together:

Testosterone is kept steady by negative feedback. When testosterone rises above its normal level, it inhibits the release of FSH and LH from the pituitary. Less stimulation means less testosterone is produced, so the level falls back to normal. This continuous self-correction keeps testosterone and sperm production stable, unlike the cyclical pattern seen in females.

The menstrual cycle: the follicular phase

The cycle begins with the follicular phase:

• FSH from the pituitary stimulates a follicle in the ovary to develop, and stimulates the follicle to secrete oestrogen.
• Oestrogen causes the endometrium (lining of the uterus) to repair and thicken, ready for a possible pregnancy.
• As the follicle matures, oestrogen rises to a peak. High oestrogen now acts by positive feedback, triggering a sharp surge of LH from the pituitary.
• The LH surge causes ovulation, the release of the mature ovum from the follicle, at about the middle of the cycle.

The menstrual cycle: the luteal phase

After ovulation, the luteal phase follows:

• LH causes the remains of the follicle to develop into a corpus luteum.
• The corpus luteum secretes progesterone (and some oestrogen). Progesterone maintains the thick endometrium, keeping it ready to receive a fertilised egg.
• High progesterone and oestrogen together inhibit FSH and LH by negative feedback, which prevents further follicles developing during the rest of the cycle.

If the ovum is not fertilised, the corpus luteum breaks down, so progesterone falls. Without progesterone the endometrium can no longer be maintained, and it is shed as menstruation. The fall in progesterone also removes the inhibition of FSH, so FSH rises again and a new cycle begins.

Examples in context

Example 1. Pregnancy and the corpus luteum. If fertilisation occurs, the developing embryo releases a hormone that keeps the corpus luteum alive, so progesterone stays high and the endometrium is maintained. This prevents menstruation and is the basis of how pregnancy tests detect that hormone.

Example 2. Negative feedback steadying testosterone. If testosterone is given as a drug, the raised level inhibits FSH and LH so strongly that the body's own sperm production can fall. This unwanted effect on athletes who misuse testosterone shows negative feedback in action.

Try this

Q1. Name the hormone whose surge triggers ovulation. [1 mark]

• Cue. LH (luteinising hormone).

Q2. Explain why menstruation occurs when the corpus luteum breaks down. [1 mark]

• Cue. The corpus luteum makes progesterone, which maintains the endometrium; when it breaks down, progesterone falls and the lining is shed.