Prolactin

What hormone is responsible for milk letdown?

Oxytocin

What is the hypothalamic releasing hormone responsible for lactogenesis?

Prolactin releasing hormone - PRH

What cell of the anterior pituitary is related to releases prolactin?

Lactotroph

What is the target tissue for prolactin?

Mammary glands

What is the hypothalamic hormone responsible for inhibiting prolactin?

Dopamine

What is dopamine’s target tissue when inhibiting the release of prolactin?

Lactotrophs

What mechanism does PRH use?

Phospholipase C

What do lactotrophs secrete?

Prolactin - peptide hormone

What is the function of prolactin?

Mammary gland development and milk production

What inhibits the adenylyl cyclase activity involved in inhibition of prolactin?

Dopamine D2 receptor

What mechanism does prolactin use?

Tyrosine kinase

Why are blood levels of prolactin low in nonlactating females and in males?

Dopamine levels

When do blood levels of prolactin increase?

During pregnancy and lactation

What are the result of prolactin in mammary glands?

Proliferation, differentiation, and lactogenesis

What nuclei releases PRH/TRH/PRF?

Paraventricular nuclei

What nucleus releases dopamine/PIH?

Arcuate nuclei

What are the three major components of milk in mammary glands?

Lactose - carbohydrate

Casein - protein

Lipids

How does prolactin stimulate milk production?

Inducing synthesis of components of milk in the mammary

What is the major action of prolactin?

Stimulation of milk production and secretion in response to suckling

Why does lactation not occur during pregnancy despite high prolactin levels?

High levels of estrogen and progesterone down-regulate prolactin receptors in the breast and block prolactin’s actions

T/F: Estrogen and progesterone levels increase and then prolactin can stimulate lactogenesis.

False - levels decrease and so do their inhibitory actions

What kind of feedback loop is prolactin as the baby suckles?

Positive - baby suckles, mammary glands are stimulated to produce milk, baby suckles more

When does prolactin, along with estrogen and progesterone, stimulate proliferation and branching of mammary glands?

Puberty

What does prolactin, with estrogen and progesterone, stimulate at puberty?

Proliferation and branching of mammary glands

What does prolactin stimulate during pregnancy?

Growth and development of mammary alveoli

What produces milk once parturition occurs?

Mammary alveoli

What can abnormal pressure on the pituitary gland or damage cause?

Hypopituitarism

What is the result of a prolactin deficiency?

Failure to lactate after giving birth

What is the MC cause of prolactin deficiency?

Sheehan syndrome

What are the defining features of Sheehan syndrome?

Postpartum pituitary necrosis due to excess blood loss during/after childbirth

What are the top 3 causes of hypopituitarism?

Sheehan Syndrome

Head injury

Infections

What is the result of destruction of the arcuate nuclei?

Less dopamine/PIH

What are some causes of increased prolactin?

Destruction of arcuate nuclei

Interruption of hypothalamic/hypophyseal tract

Over-active paraventricular nuclei or prolactinomas

T/F: Increase of TRH causes prolactin levels to rise.

True

What are the two main symptoms of excess prolactin secretion?

Galactorrhea and infertility (caused by inhibition of GnRH secretion by high prolactin levels)

What can treat increased prolactin levels?

Bromocriptine - dopamine agonist

How does high prolactin levels inhibit ovulation?

Inhibit synthesis/release of GnRH

What is the result of high prolactin inhibiting the release of GnRH?

Decreased FSH and LH