Tag: follicle-stimulating hormone

Luteinising hormone (LH) is one of the key hormones involved in the regulation of the menstrual cycle and ovulation. But what happens when our levels get a little off balance? In this article, we’ll explain exactly what luteinising hormone is, how it works, and take a deep dive into its importance for female fertility. We’ll also take a look at LH levels and why they’re important, as well as how to recognise the symptoms of low or high LH. Quick facts: What is Luteinising Hormone (LH)?  Luteinising hormone is a hormone made by the pituitary gland in the brain. It forms part of a communication system between your brain and reproductive organs known as the hypothalamic-pituitary-gonadal axis (HPG axis). The hypothalamus (also in the brain) makes gonadotrophin-releasing hormone (GnRH), which tells the pituitary gland to make two key reproductive hormones: luteinising hormone (LH) and  LH and, follicle-stimulating hormone (FSH). These two hormones work closely together. FSH helps the follicles (the small sacs in your ovaries containing immature eggs) develop during the first half of the menstrual cycle. LH then becomes particularly important around the middle of the cycle, when a sharp rise in LH helps trigger ovulation, the release of a mature egg from the ovary. What does luteinising hormone do during the menstrual cycle? Luteinising hormone (LH) works alongside FSH and oestradiol to coordinate the menstrual cycle and regulate ovulation. At the beginning of the cycle, LH levels are relatively low. During this follicular phase, FSH helps several follicles (the sacs with the immature eggs) begin developing. As one follicle becomes dominant, it produces increasing amounts of oestradiol. The rise in oestradiol tells your pituitary gland to stop making FSH and to start making more LH. This is known as the LH surge. The LH surge helps the egg complete its final maturation and triggers the dominant follicle to rupture, releasing the egg from the ovary. This process is called ovulation. After ovulation, LH levels fall as the cycle enters the luteal phase. LH helps the emptied follicle develop into the corpus luteum, which produces progesterone alongside oestradiol. These hormones help prepare and maintain the uterine lining in case pregnancy occurs. If pregnancy doesn’t occur, the corpus luteum eventually breaks down. Progesterone and oestradiol levels fall, your period begins and the cycle starts again. You can read more about how all of these hormones work together in our Menstrual Cycle 101 guide. What is the LH surge? The LH surge is a rapid rise in luteinising hormone that happens shortly before ovulation. This is exactly what at home ovulation predictor kits, or OPKs, are designed to detect. Urinary LH tests can identify the mid-cycle surge that generally occurs around 24-36 hours before ovulation, which is why they can be useful for identifying when your fertile window may be approaching. But an LH surge predicts that ovulation may happen. It doesn’t prove that an egg was actually released. How does luteinising hormone affect fertility? LH is essential for fertility because it helps coordinate ovulation. Without appropriate LH signalling, the final stages of follicle maturation and egg release may not happen. But this doesn’t mean a single LH result can tell you whether you are fertile. Fertility depends on many factors, including your age, whether you’re ovulating, ovarian reserve, fallopian-tube and uterus health, sperm health and whether underlying health conditions such as endometriosis or PMOS are present. LH is therefore usually interpreted as one part of the fertility picture. Current NICE guidance recommends measuring FSH and LH in people with irregular menstrual cycles who are undergoing fertility investigation, helping doctors understand whether disrupted ovulation may be part of the problem. If you’re tracking ovulation at home, LH can also help identify when your fertile window may be approaching, although, again, it can’t confirm ovulation by itself. Why do I need an LH test? An LH test can be useful for several different reasons. One of the most common is investigating irregular or absent periods. Because LH is involved in ovulation, looking at it alongside hormones such as FSH and oestradiol can give clues about how the communication between your brain and ovaries is working. LH may also be measured if you’re having difficulty conceiving, particularly if your cycles are irregular or there is reason to think you might not be ovulating consistently. It can also form part of the investigation of conditions such as PMOS, hypothalamic amenorrhoea, primary ovarian insufficiency or pituitary disorders, although LH cannot diagnose any of these conditions on its own. For example, lower LH and FSH alongside low oestradiol can point towards reduced signalling from the hypothalamus or pituitary gland, while raised gonadotrophins alongside low ovarian hormone levels can suggest reduced ovarian function. LH testing is therefore most useful when it is interpreted alongside your symptoms, menstrual-cycle pattern and other hormone results. How can I find out my LH level? LH can be measured through a blood test or, for ovulation tracking, through a urine test. A blood test measures the amount of LH circulating in your bloodstream. This is usually the more useful approach when LH is being investigated as part of a wider hormone assessment. Urinary ovulation tests have a different purpose. They’re designed specifically to detect the rise in LH that happens shortly before ovulation. Standard OPKs generally show a positive or negative result once LH passes a particular threshold, while some digital or quantitative monitors show more information about changing urinary LH levels. Can an LH test tell you if you’re ovulating? An LH blood test can measure how much LH is circulating at one moment in time. An ovulation predictor kit measures LH in urine and looks for the surge that usually happens before ovulation. A positive ovulation test therefore suggests that ovulation may be approaching. But LH testing doesn’t directly confirm that an egg was released. For clinical confirmation of ovulation, mid-luteal progesterone is generally more useful. If you have PMOS and are using LH strips, interpretation can be trickier […]