Understanding my LH surge

The myLotus personalised fertility tracker monitors the concentration of LH (luteinising hormone) in urine as a way to identify your fertile window – the time of the month when pregnancy can happen. However, not all LH surges look the same.

In this article, we talk about the importance of LH in the reproductive cycle, and the different types of LH surges.

The role of LH in reproduction

During the follicular phase of the ovarian cycle, the follicles and eggs start developing. When the amount of oestrogen reaches a threshold level (greater than 200 pg/ml for approximately 50 hr), a positive feedback mechanism works on the hypothalamus and anterior pituitary gland, which results in an abrupt secretion of LH (luteinising hormone) into the bloodstream.

The onset of the LH surge precedes ovulation by 35–44 hr, and the peak blood level of LH precedes ovulation by 10–12 hr. The LH surge triggers the egg to fully mature and to be released from the follicle.

A study of 155 cycles from 35 women demonstrated that the onset of the LH surge primarily occurs between midnight and early morning (37% between 00:00 and 04:00, 48% between 04:00 and 08:00). As blood containing LH is naturally filtrated in the kidneys, LH will be present in urine from mid-morning. The LH surge concentration in urine ranges from 20 to 100 mIU/ml. This midcycle LH surge is a crucial feature of the ovarian cycle because it is required for ovulation to happen.

Types of LH surge

A study looked at the characteristics of urinary LH and found that not all women are the same. LH surges that result in ovulation can varying configuration, amplitude, and duration.

The onset of the LH surge can be one of two types:

• Rapid onset, when it occurs within 1 day (42.9%)
• Gradual onset, when it occurs within 2 to 6 days (57.1%)

(Image from Park. Characteristics of urinary LH surge. Fertil Steril 2007.)

There are three types of configurations of LH surges:

• spike, in which all values after the LH peak were less than that of the LH peak (41.9%)
• biphasic, in which the first significant LH rise was followed by a decrease, then an increase, in LH concentration, which may or may not be greater than that of the first LH rise (44.2%)
• plateau, in which LH levels remained at peak values for 2 to 3 days before decreasing (13.9%)

(Image from Park. Characteristics of urinary LH surge. Fertil Steril 2007.)

Despite different onsets and configurations, the descending limbs of all LH surges have a gradual decrease to baseline. As you monitor your cycle with the myLotus personalised fertility tracker, you'll learn more about your LH pattern. Start testing on day 8 of the menstrual cycle and continue testing until you notice an increase in LH. Continue testing until the values drop to baseline. The duration of your LH surge can be between 3 to 11 days however it is the onset of the curve that determines ovulation, which usually takes place within 12 to 24 hours. A low LH peak of 2.5 fold the median value of baseline, is enough to trigger ovulation – which means you don’t need very high values to ovulate!

The myLotus personalised fertility tracker will detect your LH values even if they are low (unlike other LH tests which only test positive when you reach a determined threshold value). Not all women are the same, and what is usually accepted as a standard cycle, does not reflect the majority of women. Using the myLotus personalised fertility tracker will allow you to get to know your cycle, your levels and your peak fertile days.