What are the functions of the prolactin and oxytocin hormones? | Diagnostic Agent - Sharecare
Prolactin (PRL), also known as luteotropic hormone or luteotropin, is a protein that is best known for its role in enabling mammals, usually females, to produce milk. It is influential in over separate processes in various vertebrates, including humans. Prolactin is secreted from the pituitary gland in response to eating, mating, . The suckling stimulus also triggers. The possible participation of oxytocin in the regulation of pituitary LtH secretion was studied by comparing the retarding effects of these hormones on mammary. J Psychosom Obstet Gynecol ; Oxytocin, prolactin, milk production and their relationship with personality traits in women after vaginal delivery or.
Abstract In the female rat, a complex interplay of both stimulatory and inhibitory hypothalamic factors controls the secretion of prolactin.
What are the functions of the prolactin and oxytocin hormones?
Prolactin regulates a large number of physiological processes from immunity to stress. In the following review, we have chosen to focus on the control of prolactin secretion in the female rat in response to suckling, mating and ovarian steroids. In all three of these states, dopamine, released from neurones in the mediobasal hypothalamus, is a potent inhibitory signal regulating prolactin secretion.
Early research has determined that the relief of dopaminergic tone is not enough to account for the full surge of prolactin secretion observed in response to the suckling stimulus, launching a search for possible prolactin-releasing factors.
This research has since broadened to include searching for prolactin-releasing factors controlling prolactin secretion following mating or ovarian steroids. A great deal of literature has suggested that this prolactin-releasing factor may include oxytocin. Oxytocin receptors are present on lactotrophs. These oxytocin receptors respond to exogenous oxytocin and antagonism of endogenous oxytocin inhibits lactotroph activity. In addition, the pattern of oxytocin neuronal activity and oxytocin release correlate with the release of prolactin.
Here we suggest that not only is oxytocin stimulating prolactin secretion, but we also hypothesize that prolactin secretion is controlled by a complex network of positive oxytocin and negative dopamine feedback loops.
You and Your Hormones
In the present review, we will discuss this literature and attempt to describe the circuitry we believe may be responsible for controlling prolactin secretion. Prolactin, so named for its ability to stimulate lactation and mammary gland development, is a protein hormone which is primarily synthesized in and secreted from lactotrophs in the anterior pituitary gland 1.
In rats, the translation of the prolactin gene results in a amino acid polypeptide 2which influences over physiological events including osmoregulation, immunomodulation, behaviour, reproduction, growth and development 3. Although prolactin exerts its effects on a number of biological events, the physiological control of its secretion is not wholly defined. Furthermore, while prolactin plays an undeniable role in pregnancy and stress, the role of oxytocin in these states is not yet clear.
Therefore, in the following sections, we focus on the control of prolactin secretion in response to suckling, mating and ovarian steroids. Prolactin Secretion Prolactin is secreted 1 in response to suckling 2 in response to mating and 3 on pro-oestrus evening in response to ovarian steroids 3 Fig.
The physiological basis of breastfeeding - Infant and Young Child Feeding - NCBI Bookshelf
It has been hypothesized that in vertebrates such as mice a similar tissue-specific effect is achieved by a large family of prolactin-like proteins controlled by at least 26 paralogous PRL genes not present in primates. Prolactin levels peak during REM sleep and in the early morning. Many mammals experience a seasonal cycle. During pregnancyhigh circulating concentrations of estrogen and progesterone increase prolactin levels by to fold.
Estrogen and progesterone inhibit the stimulatory effects of prolactin on milk production. The abrupt drop of estrogen and progesterone levels following delivery allow prolactin—which temporarily remains high—to induce lactation. The sucking activates mechanoreceptors in and around the nipple. These signals are carried by nerve fibers through the spinal cord to the hypothalamuswhere changes in the electrical activity of neurons that regulate the pituitary gland increase prolactin secretion.
The suckling stimulus also triggers the release of oxytocin from the posterior pituitary glandwhich triggers milk let-down: Prolactin controls milk production lactogenesis but not the milk-ejection reflex; the rise in prolactin fills the breast with milk in preparation for the next feed. In usual circumstances, in the absence of galactorrhealactation ceases within one or two weeks following the end of breastfeeding. Levels can rise after exercise, high-protein meals, minor surgical procedures,  following epileptic seizures  or due to physical or emotional stress.
Hyperprolactinemia is the most frequent abnormality of the anterior pituitary tumors, termed prolactinomas.
Oxytocin: An emerging regulator of prolactin secretion in the female rat
Prolactinomas may disrupt the hypothalamic-pituitary-gonadal axis as prolactin tends to suppress the secretion of GnRH from the hypothalamus and in turn decreases the secretion of follicle-stimulating hormone FSH and luteinizing hormone LH from the anterior pituitary, therefore disrupting the ovulatory cycle.
Inappropriate lactation galactorrhoea is another important clinical sign of prolactinomas. Structure and isoforms[ edit ] The structure of prolactin is similar to that of growth hormone and placental lactogen. The molecule is folded due to the activity of three disulfide bonds. Significant heterogeneity of the molecule has been described, thus bioassays and immunoassays can give different results due to differing glycosylationphosphorylation and sulfationas well as degradation.