Hormones and Reproduction
There are numerous hormones that play important roles in human reproduction. Of these, luteinizing hormone (LH) is perhaps the most important as far as conception goes.
In the female body, luteinizing hormone and follicle stimulating hormone work together to agitate follicles within the ovaries. One follicle becomes dominant, while the others wither and die. As the follicle reaches maturation, there is a surge in LH, triggering the follicle to burst and release an egg into the fallopian tubes. The follicle, meanwhile, becomes a 'corpus luteum', producing progesterone to thicken the endometrium within the uterus.
LH supports the luteal function of pregnancy for the first two weeks, gradually replaced by the functions of human Chorionic Gonadotropin (hCG). LH is also integral in the support of ovarian thecal cells, providing androgen and the hormonal 'building blocks' of an estrogen hormone.
Measuring Fertility and Determining Pregnancy
Women who have been attempting conception for some time may use ovulation tests and home pregnancy tests to determine their reproductive "status". Ovulation tests base their readings off of the level of LH in the woman's urine, whereas home pregnancy tests measure the amount of hCG.
The female body does not naturally produce HCG, except in cases of rare liver disease and some cancers. Therefore, any amount of hCG detected by home pregnancy tests could be said to be significant. Home pregnancy tests usually detect hCG levels in excess of 20mlU/mL, although some women don't produce that amount until they've been pregnant for two to four weeks.
The Origin of hCG
After the egg is fertilised and implanted in the endometrium, the beginning layers of what will become the placenta release hCG into the bloodstream. HCG has many similar characteristics to LH and follicle stimulating hormone, and it works together with these hormones to nourish and support embryonic growth. As hCG is produced within a few hours of implantation, early home pregnancy tests boast they can accurately detect pregnancy within just a few days. However, even home pregnancy tests designed for 'early' use don't often have a higher sensitivity than the levels stated previously.
Trying to conceive can be difficult and stressful, especially during repeated attempts and negative results on home pregnancy tests. Some women develop an aversion to home pregnancy tests entirely - and this may be a good thing, especially if they're taking hormone-based fertility medication. Some fertility medications are created using hCG or LH, which can affect the accuracy of home pregnancy tests.
The most accurate pregnancy test - more accurate than any available home pregnancy tests - is the quantitative blood test available from your doctor. This test can detect hCG levels of less than 1mlU/mL, which puts the sensitivity of home pregnancy tests to shame. If you believe you may be pregnant and you're sick of using home pregnancy tests, contact your doctor instead.