These hormones are responsible for the regulation of the reproductive cycle in both women and men. They work regulating the male gonadal activity (testes) and the female gonadal activity (ovaries and endometrium).
The majority of these hormones are shared by men as well as women, although in different amounts. For instance, testosterone or androgens are typical male hormones; however, they are also present in women but only to a very small extent.
Hypothalamic–pituitary–adrenal axis (HPA axis)
Hormone production is operated by brain signals sent to the glands. As for sex or reproductive hormones, they are released by the hypophysis (pituitary gland) thanks to the hypothalamic action. The hypothalamus is a portion located at the base of the brain and is the primarily controller of multiple vegetative functions.
The pituitary gland is attached to the hypothalamus via a small tube called the “pituitary stalk” (a.k.a. the “infundibular stalk” or the “infundibulum”) and it is divided into different regions:
- Adenohypophysis or anterior pituitary: it comprises the anterior, largest lobe of the pituitary gland. It operates depending on the stimuli it receives from the hypothalamus, which releases hormones such as GnRH (gonadotropin-releasing hormone) in order to trigger the production of adenohypophysis and others to inhibit it.
- Neurohypophysis or posterior pituitary: it comprises the posterior lobe of the pituitary gland. It releases hormones such as vasopressin or oxytocin into the bloodstream.
Male sex hormones
In this section we will be focusing on the testes and the seminiferous tubule. The latter are structures located within the testes and are responsible for sperm production.
- FSH hormone (follicle-stimulating hormone): it regulates the action of the Sertoli cells (a type of cells located within the seminiferous tubule).
- LH hormone (luteinizing hormone): it regulates the action of the Leydig cells (another type of cells located within the seminiferous tubule).
- Testosterone: this hormone is product of estradiol and is responsible for the development of the male genitalia (penis and testes) and the appearance of the secondary sexual characteristics.
Female sex hormones
There are hormones responsible for the development of the female genitalia and the secondary sexual characteristics as well as affecting the menstrual cycle.
- Oestrogens: it is the main female hormone, since it is responsible for the development of the female genitalia (ovaries, womb, and vagina) and the secondary sexual characteristics, as well as the appearance of the menstrual cycle.
- Progesterone: it is responsible for the endometrial thickening which takes place during the menstrual cycle in order to allow embryo implantation within the woman’s womb in case fertilisation occurs.
- FSH hormone: it stimulates follicle development. Follicles are structures found in the ovaries containing the oocytes or eggs.
- LH hormone: it has basal levels during the whole menstrual cycle, although the LH peak occurs on day 14th, triggering thus oocyte release, that is to say, ovulation.