LUF: Fertile Thoughts
by Carlene W. Elsner MD
Q: How is the luteinized unruptured follicle syndrome usually diagnosed and how common is it?
A: The luteinized unruptured follicle (LUF) syndrome is a rare condition in which all the hormonal events of a normal ovulatory cycle occur but the ovum is not physically released from the follicle on the ovary so pregnancy does not occur. The diagnosis of LUF is an ultrasound diagnosis.
In a normal cycle, there are several indirect indicators of ovulation; a biphasic basal body temperature (BBT) chart, a post ovulatory progesterone level greater than 2 ng/ml, and disappearance of the follicle on the ovary determined by ultrasound. The only direct indicators of ovulation having occurred are the establishment of a pregnancy or actual visualization of the release of the egg such as at the time of laparoscopy. Obviously the second of these direct indicators rarely is available.
Eggs develop in follicles on the ovary, one egg to each follicle. As the follicle grows, the follicle wall begins to thin out. When the follicle is about 2 cm in size and the egg inside is mature, the follicle wall becomes very thin and eventually ruptures, releasing the egg that is then picked up by the fimbria of the tube. If disappearance of the follicle is documented on ultrasound, then the diagnosis of LUF is ruled out because the presumption is that the follicle has ruptured and the egg has been released. If in a cycle, a woman’s BBT shows a sustained temperature elevation and her progesterone rises above two, but the lead follicle on her ovary does not collapse as expected, then the diagnosis of LUF can be considered.
LUF is a difficult diagnosis to make because sometimes, even though the egg has been released from the follicle, the follicle will refill with blood so on ultrasound, it appears that the follicle is still there and has not ruptured. After the egg has been released from the follicle, the follicle then begins to produce progesterone and becomes the corpus luteum. Sometimes these corpus lutea can appear cystic on ultrasound. These cystic corpus lutea can in some cases look a lot like a follicle.
Women who have been pregnant before probably do not have LUF. The treatment of LUF is invitro fertilization (IVF) because when you do IVF, a needle is introduced into the follicle to retrieve the egg, so rupture of the follicle is not necessary to establish a pregnancy.
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