Among other uses, scientists use this technology in infertility treatments to create hormones that have the same DNA structure as the ones in our bodies. Even though these hormones are created in a lab, they are bio-identical to the real thing. Bio-identical means they have the same molecular shape and structure as the natural hormones in our bodies, and our bodies react to them in the same way as the real thing.
At one time, the only source for gonadotropins (fertility drugs which contain hormones like FSH and LH) was by extracting and purifying the hormones from the urine of post-menopausal or pregnant women. For example, post-menopausal women have high levels of the hormone FSH, making their urine a good source. Pregnant women have high levels of the hormone hCG, also known as the pregnancy hormone. hCG acts similarly to LH in the body, and is used during some fertility treatments to stimulate ovulation.
The problem with this method is it was difficult to maintain consistency from batch to batch, and also, the urinary proteins couldn’t be 100% removed, leading to allergic reactions in some. Hormones in fertility drugs created with recombinant DNA technology are completely free from urinary proteins, and are considered to be more effective at lower doses than urinary-extracted products.
Still today, the source for many hormonal medications is extraction and purification from urine, like with Bravelle and Ovidrel. However, thanks to recombinant DNA technology, more hormonal treatments can be created in the lab. Examples include Gonal-F and Follistim.
You can read more about fertility drugs here.