36 Questions
What is the main role of prolactin in mammals?
Enabling milk production
When is prolactin secreted from the pituitary gland?
In response to eating, mating, and nursing
In what manner does prolactin act as a growth factor?
Influencing hematopoiesis and angiogenesis
When was prolactin confirmed in humans?
Around 1970
What is the source of prolactin in response to various events?
Pituitary gland
What is the function of prolactin in fish?
Controlling water balance
How does prolactin act in endocrine, autocrine, and paracrine manners?
Through the prolactin receptor and numerous cytokine receptors
In what manner does prolactin act as an important regulator of the immune system?
By acting as an anti-apoptotic factor
What is the main function of prolactin in pancreatic development?
Supporting cell differentiation
What is the primary influence of prolactin on metabolism?
Promoting fat storage
Which event triggers heavy secretion of prolactin?
Estrogen treatment
How does prolactin influence cell cycle-related functions?
By inhibiting cell death (apoptosis)
What stimulates extrapituitary prolactin production?
cAMP
Which hormone temporarily remains high after delivery to induce lactation?
Prolactin
During pregnancy, what increases prolactin levels by 10- to 20-fold?
Progesterone
What triggers the release of oxytocin from the posterior pituitary gland?
Sucking on the nipple
Which neuropeptide is a powerful prolactin-releasing factor in birds (turkeys)?
VIP
What hormone does not play a large role in raising prolactin levels in mice without a posterior pituitary?
Oxytocin
What do mice react to in terms of prolactin-releasing neuropeptides?
VIP and TRH
What is responsible for stimulating extrapituitary prolactin production?
cAMP–responsive element
What hormone upregulates prolactin synthesis in the endometrium but decreases it in myometrium and breast glandular tissue?
Progesterone
What does VIP act as in birds (turkeys)?
Powerful prolactin-releasing factor
What follows diurnal and ovulatory cycles?
Prolactin levels
What hormone inhibits the stimulatory effects of prolactin on milk production?
Estrogen
What is the principal control of thyrotropin-releasing hormone on prolactin release?
Inhibitory
Where are prolactin and its receptor expressed in the skin?
In hair follicles
What is the main function of prolactin in fish?
Osmoregulation
Which hormone inhibits prolactin production through Pit-1 transcription factor?
Dopamine
What is the effect of prolactin on mammary glands during puberty and pregnancy?
Stimulates growth
How does prolactin affect lipid synthesis in mammary and adipose cells?
Stimulates in both mammary and adipose cells
What effect does slightly elevated prolactin levels have on estrogen levels in humans?
No effect on estrogen levels
What is the effect of prolactin on luteinizing hormone-receptors in Leydig cells?
Activates the receptors
What triggers pituitary prolactin secretion?
Thyrotropin-releasing hormone
What is the function of prolactin in birds?
Affecting crop milk production
Where is prolactin produced in humans?
Breast
What is the effect of prolactin on myelin coatings on axons in the central nervous system?
Stimulates myelin formation
Study Notes
- Pituitary prolactin secretion is regulated by neurons in the hypothalamus, specifically neurosecretory tuberoinfundibulum (TIDA) neurons of the arcuate nucleus.
- TIDA neurons secrete dopamine (Prolactin Inhibitory Hormone) to act on lactotrophs' D2 receptors, inhibiting prolactin secretion.
- Thyrotropin-releasing hormone stimulates prolactin release, but it is the only anterior pituitary hormone whose principal control is inhibitory.
- Prolactin has multiple roles and forms. In humans, there are 14, 16, and 22 kDa variants, and it is closely related to somatolactin.
- Prolactin stimulates mammary glands to produce milk and has effects on maternal behavior. It affects lipid synthesis differently in mammary and adipose cells and may affect sex hormone levels.
- Prolactin inhibits gonadotropin-releasing hormone secretion but its exact mechanism is unknown.
- In humans, prolactin enhances luteinizing hormone-receptors in Leydig cells, leading to testosterone secretion.
- Prolactin stimulates oligodendrocyte precursor cells to form myelin coatings on axons in the central nervous system.
- In fish, prolactin's primary function is osmoregulation but it also has reproductive functions.
- Prolactin in fish controls the production of skin secretions and regulates hair growth and moulting in an autocrine fashion.
- Prolactin receptor activation is essential for normal mammary gland development during puberty and pregnancy in mammals.
- Prolactin is produced in multiple locations including the anterior pituitary, decidua, myometrium, breast, lymphocytes, leukocytes, and prostate.
- Pituitary prolactin production is controlled by the Pit-1 transcription factor, which is inhibited by dopamine and stimulated by estrogens, neuropeptides, and growth factors.
- Estrogens can suppress dopamine, and Thyrotropin-releasing hormone stimulates prolactin secretion.
- Prolactin functions include lactation, maternal behavior, osmoregulation, and regulating sex hormones and hair growth.
- In humans, slightly elevated prolactin levels can have variable effects on estrogen levels.
- Prolactin has roles in reproduction, parental care, and pulmonary surfactant synthesis.
- Prolactin and its receptor are expressed in the skin, specifically in hair follicles.
- Prolactin has effects on feathering and crop milk production in birds.
- Prolactin may play a role in the pleasurable perception of sad music in music psychology.
- Prolactin can initiate pseudopregnancy in rodents.
- Prolactin receptor activation is essential for normal mammary gland development and that adult virgin female prolactin receptor knockout mice have much smaller and less developed mammary glands.
Test your knowledge about the function and secretion of prolactin, a protein responsible for enabling mammals to produce milk and influencing over 300 processes in various vertebrates, including humans. Learn about its role in metabolism, immune system regulation, and more.
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