Luteolysis
Encyclopedia
Luteolysis is the structural and functional degradation of the corpus luteum
(CL), which occurs at the end of the luteal phase
of both the estrous
and menstrual cycles
in the absence of pregnancy
. In domestic animals, luteolysis is inititated by the hormones prostaglandin F2alpha and oxytocin
. In sheep, communication between the pars nervosa (posterior lobe of the pituitary gland), corpus luteum, and the uterus endometrium
via the circulatory system is required for luteolysis. Studies with sheep have found that, if the uterine horn ipsalateral to the ovary possessing the CL is surgically removed, the lifespan of the corpus luteum will increase drastically.
Luteolysis in primates (including humans), however, is not caused by prostaglandin, and removal of the uterus will not prolong the life of the corpus luteum. However, primates do respond to PGF2a, and women and asthmatics should take great care when handling this hormone.
Oestrogen
and primarily progesterone
, secreted by the corpus luteum, inhibit the release of Luteinizing hormone
(LH) by the adenohypophysis (anterior lobe of the pituitary gland) via classical negative feedback mechanisms. This removes the luteotrophic support provided by the gonadotropin Luteinizing Hormone (LH), and the corpus luteum degrades to a corpus albicans
(scar tissue), which is eventually absorbed into the ovary.
Degradation of the corpus luteum will result in reduced levels of progesterone, promoting an increase in follicle-stimulating hormone
(FSH) secretion by the adenohypophysis, which will trigger the development of a new follicle
on the ovary
.
If pregnancy occurs, the placental hormone chorionic gonadotrophin continues to maintain the corpus luteum, but in some species it will eventually degrade sometime during pregnancy.
Corpus luteum
The corpus luteum is a temporary endocrine structure in mammals, involved in production of relatively high levels of progesterone and moderate levels of estradiol and inhibin A...
(CL), which occurs at the end of the luteal phase
Luteal phase
The luteal phase is the latter phase of the menstrual cycle or the estrous cycle . It begins with the formation of the corpus luteum and ends in either pregnancy or luteolysis...
of both the estrous
Estrous cycle
The estrous cycle comprises the recurring physiologic changes that are induced by reproductive hormones in most mammalian placental females. Estrous cycles start after puberty in sexually mature females and are interrupted by anestrous phases or pregnancies...
and menstrual cycles
Menstrual cycle
The menstrual cycle is the scientific term for the physiological changes that can occur in fertile women for the purpose of sexual reproduction. This article focuses on the human menstrual cycle....
in the absence of pregnancy
Pregnancy
Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...
. In domestic animals, luteolysis is inititated by the hormones prostaglandin F2alpha and oxytocin
Oxytocin
Oxytocin is a mammalian hormone that acts primarily as a neuromodulator in the brain.Oxytocin is best known for its roles in sexual reproduction, in particular during and after childbirth...
. In sheep, communication between the pars nervosa (posterior lobe of the pituitary gland), corpus luteum, and the uterus endometrium
Endometrium
-Function:The endometrium is the innermost glandular layer and functions as a lining for the uterus, preventing adhesions between the opposed walls of the myometrium, thereby maintaining the patency of the uterine cavity. During the menstrual cycle or estrous cycle, the endometrium grows to a...
via the circulatory system is required for luteolysis. Studies with sheep have found that, if the uterine horn ipsalateral to the ovary possessing the CL is surgically removed, the lifespan of the corpus luteum will increase drastically.
Luteolysis in primates (including humans), however, is not caused by prostaglandin, and removal of the uterus will not prolong the life of the corpus luteum. However, primates do respond to PGF2a, and women and asthmatics should take great care when handling this hormone.
Oestrogen
Estrogen
Estrogens , oestrogens , or œstrogens, are a group of compounds named for their importance in the estrous cycle of humans and other animals. They are the primary female sex hormones. Natural estrogens are steroid hormones, while some synthetic ones are non-steroidal...
and primarily progesterone
Progesterone
Progesterone also known as P4 is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy and embryogenesis of humans and other species...
, secreted by the corpus luteum, inhibit the release of Luteinizing hormone
Luteinizing hormone
Luteinizing hormone is a hormone produced by the anterior pituitary gland. In females, an acute rise of LH called the LH surge triggers ovulation and development of the corpus luteum. In males, where LH had also been called interstitial cell-stimulating hormone , it stimulates Leydig cell...
(LH) by the adenohypophysis (anterior lobe of the pituitary gland) via classical negative feedback mechanisms. This removes the luteotrophic support provided by the gonadotropin Luteinizing Hormone (LH), and the corpus luteum degrades to a corpus albicans
Corpus albicans
The corpus albicans is the regressed form of the corpus luteum. As the corpus luteum is being broken down by macrophages, fibroblasts lay down type I collagen, forming the corpus albicans. This process is called "luteolysis". The remains of the corpus albicans may persist as a scar on the surface...
(scar tissue), which is eventually absorbed into the ovary.
Degradation of the corpus luteum will result in reduced levels of progesterone, promoting an increase in follicle-stimulating hormone
Follicle-stimulating hormone
Follicle-stimulating hormone is a hormone found in humans and other animals. It is synthesized and secreted by gonadotrophs of the anterior pituitary gland. FSH regulates the development, growth, pubertal maturation, and reproductive processes of the body. FSH and Luteinizing hormone act...
(FSH) secretion by the adenohypophysis, which will trigger the development of a new follicle
Ovarian follicle
Ovarian follicles are the basic units of female reproductive biology, each of which is composed of roughly spherical aggregations of cells found in the ovary. They contain a single oocyte . These structures are periodically initiated to grow and develop, culminating in ovulation of usually a single...
on the ovary
Ovary
The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in anatomically female individuals are analogous to testes in anatomically male individuals, in that they are both gonads and endocrine glands.-Human anatomy:Ovaries...
.
If pregnancy occurs, the placental hormone chorionic gonadotrophin continues to maintain the corpus luteum, but in some species it will eventually degrade sometime during pregnancy.