UNDERSTANDING THE MENSTRUAL CYCLE
In the Ovary
Your menstrual cycle is divided into two phases as described in the image: Follicular Phase is the stage when
the follicle development occurs, and the Luteal Phase, that happens following the ovulation.
A follicle contains either one egg or none and once the egg is released, the follicle becomes
a corpus luteum that is eventually absorbed by the tissue. This is called the luteal phase.
In the Uterus (Endometrium)
Day 1 of the cycle is when menstruation starts. Once menstruation has
finished (around day 7), the endometrium lining starts getting thicker, this is the Proliferative
Phase. The last 14 days of the cycle are part of the Secretory Phase when the endometrium thickness
achieves its peak in order to prepare the bed for an embryo - if fertilization of the egg released
Understanding fertility hormones
The Pituitary gland (also called Hypophysis) is located in the brain. It is known as the “Master gland” because its activity
affects the reproductive system and sexual behaviour.
The pituitary gland secretes Follicle-stimulating
hormone (FSH) and Luteinizing hormone (LH - 3). Once these hormones released into your bloodstream,
they work as messengers to generate the ovulation during the menstrual cycle.
Older women - or
some unfortunate younger women with reduced egg reserve - will require higher amount of FSH release
from the pituitary gland to stimulate the ovaries to produce an egg. Accordingly, high levels
of FSH from blood test may indicate reduced egg reserve. However, AMH hormone is more accurate
test for egg reserve (see below).
The female hormones are protein-based hormones
that travel to a specific area in the body – for example the ovary – and induce a specific effect
depending on their concentration and their receptivity in the tissue.
- LH – Luteinising Hormone:
responsible mainly for ovulation – egg release. It also stimulates the ovaries to secrete oestrogen.
- FSH – Follicular stimulating hormone: responsible for stimulating the ovaries to produce cells
leading to follicle development.
- PROGESTERONE – this hormone is produced following ovulation.
It is very important for the womb lining in order to promote embryo implantation. High levels
of progesterone avoid early bleeding in pregnancy.
- OESTROGEN – it is produced by the ovaries
during the menstrual cycle. It has two functions: preparing the egg to ovulate and preparing
the womb to receive the embryo implantation and consequently pregnancy. The hormone level vary
according to the phase of the cycle - reaching the peak before ovulation -, and according to
the woman’s age.
- AMH – Anti-Müllerian hormone: a hormone starts to be produced as early as
the women are inside their mother’s womb and continues up to their menopause. This hormone is
related to woman’s egg reserve and is used as a marker for infertility diagnosis.