Q.Why are menstrual cycles absent during pregnancy?

Let’s begin with an everyday picture. Think of a factory that produces a specific product — say, a car factory. The factory doesn’t just run on its own; it needs a central command centre that sends signals to start production, keep it steady, and stop it when enough cars are made. In the male body, the “factory” is the testes, and the “product” is sperm. The command centre is the brain — specifically two tiny glands: the hypothalamus and the pituitary gland. The signals they send are hormones (chemical messengers that travel through the blood).

Hormonal regulation of spermatogenesis means that the entire process of sperm production is controlled by a chain of hormones, each one triggering or suppressing the next. This ensures that sperm are made at the right time, in the right quantity, and that the body doesn’t overproduce them.

The Hormonal Chain (Step by Step)

1. Hypothalamus releases GnRH

   The hypothalamus, a region at the base of the brain, secretes Gonadotropin-Releasing Hormone (GnRH). This is the “start” signal. GnRH travels a short distance to the pituitary gland, telling it to get ready.

2. Pituitary releases two key hormones

   In response to GnRH, the anterior pituitary releases two hormones into the bloodstream:

   • LH (Luteinizing Hormone) — targets the Leydig cells in the testes.
   • FSH (Follicle-Stimulating Hormone) — targets the Sertoli cells in the seminiferous tubules (the actual “assembly line” where sperm are made).

3. LH stimulates testosterone production

   Leydig cells, when activated by LH, produce testosterone. Testosterone is the main male sex hormone and is absolutely essential for spermatogenesis. It acts directly on the seminiferous tubules to drive sperm production.

4. FSH supports the Sertoli cells

   Sertoli cells are like the “nourishers” and “quality controllers” inside the tubules. FSH makes them produce nutrients and other factors that help developing sperm cells survive and mature. Sertoli cells also convert some testosterone into a more active form.

The Feedback Loop (Why It Doesn’t Go Wild)

The body hates waste. If too much testosterone is produced, it sends a message back to the brain to slow down. This is called negative feedback.

• High testosterone in the blood signals the hypothalamus to reduce GnRH release, and the pituitary to reduce LH and FSH release.
• Low testosterone does the opposite — the brain increases GnRH, LH, and FSH to boost production.

This keeps testosterone levels within a narrow, healthy range. Sertoli cells also produce a hormone called inhibin, which specifically suppresses FSH when sperm production is adequate.

Why This Matters (Even for a Commerce/Humanities Student) …