The prominent players in the menstrual cycle are follicle-stimulating hormone (FSH), estrogen (Oova measures the urinary metabolite E3G), luteinizing hormone (LH), and progesterone (Oova measures the urinary metabolite PdG). The menstrual cycle is broken up into two primary phases, separated by ovulation (or the ovulatory phase).
Follicular phase
The start of a menstrual cycle is the period; the first day of your menstrual cycle would be the first day of your period. Menstruation is the beginning of the follicular phase.
A period indicates that you did not conceive in the previous cycle. Before the period, the endometrial lining of the uterus has thickened in preparation for nurturing a fertilized egg. If an egg is not fertilized, estrogen and progesterone are low, which results in the top layers of the thickening uterine lining breaking down and shedding.
That’s why you have your period. You shed that thick uterine lining to prepare for the process to happen again, so the body has another chance to conceive.
Around this time, the FSH levels begin to increase slightly, stimulating the development of several follicles in the ovaries. Each follicle contains an egg. Eventually, the FSH levels begin to decrease, and only one follicle continues to develop. This follicle starts to produce estrogen, the rise you start to see in the follicular phase.
Ovulation
As estrogen levels continue to increase, it signals to the brain's pituitary gland to begin releasing LH bursts. As a result, the LH levels rise, commonly known as the surge. When the LH levels peak, the egg is stimulated to be released from the ovary. This process is known as ovulation. Estrogen levels decrease during the surge.
Luteal phase
Once the egg has left the ovary, the luteal phase begins. LH and FSH levels decrease. The follicle ruptures after releasing the egg and forms a corpus luteum that produces progesterone. During most of this phase, the estrogen level is high but typically not as high as in the follicular phase.
Progesterone and estrogen cause the uterus lining to thicken more to prepare for possible fertilization. If the egg is not fertilized, the corpus luteum will break down and no longer produce progesterone, the estrogen level will decrease, and a period will occur. If the egg is fertilized, the corpus luteum continues to function during early pregnancy to help maintain the pregnancy.
What Oova measures
Oova measures LH, PdG (a progesterone metabolite), and E3G (an estrogen metabolite). These three hormones are critical to each phase, which means that by measuring them, you get a full picture of what's happening during your cycle.