Lecture 19 - Prolactin

What is the role of the posterior pituitary?

It releases oxytocin to stimulate milk ejection

What is the role of the anterior pituitary?

Releases prolactin to stimulate milk production

What cell is prolactin produced by?

Lactotrophs in anterior pituitary gland

Is prolactin highest in the morning or night?

Morning because it is diurnal variation

How is prolactin regulated?

Dopamine prevents release of prolactin and dopamine inhibition will allow for prolactin secretion

What other hormones can stimulate prolactin release?

trh and estrogen

What is hyperprolactinemia?

Over production of prolactin

What can cause hyperprolactinemia?

Pituitary tumor, primary hypothyroidism, macroprolactin

What are clinical symptoms of hyperprolactinemia?

Galactorrhea (breast discharge), menstrual dryness, erectile dysfunction

How is hyperprolactinemia diagnosed?

Increased prolactin in immunassys, screen for macroprolactin, tumours

Which cells secrete growth hormone?

Somatotrophic cells in anterior pituitary

What are the functions of GH?

Tissue and bone growth, stress repsonse, rasies glucose and free fatty acid conc

What biomarker is used to measure GH and why?

Insulin-like growth factor-I (IGF-I) because Gh has a very short half-life

How is GH regulated?

It is a negative loop where GH will promote growth by stimulating liver to release IGF-I causing it to suppress GH production

How is IGF-I meaured in the lab?

Chemiluminescence immunoassay

What can cause excess GH?

Pituitary hormones, lesions, GHRH producing tumours

What are clinical symptoms of excess GH?

Soft tissue and bone overgrowth

What is the first step in excess GH tesitng?

Measure serum IGF-1

What is the second step in excess GH testing?

Glucose suppression test

WHat is the glucose suppresion test?

Patients that are fasting will be given glucose to see if GH release was suppressed. Failure to suppres is indicative of acromegaly

What can cause a growth hormone deficiency?

Pituitary or hypothalamic abnormalities or GH insensitivty

How is GH deficiency tested?

Look at IGF-1 levels, then exercise stimulation, then insulin tolerance test