anterior pituitary hormones

Question 1

list anterior pituitary hormones

Answer 1

• thyroid stimulating hormone (TSH/thyrotropin)
• adrenocorticotropin hormone (ACTH/corticotropin)
• growth hormone (GH/somatotroin)
• prolactin (PRL)
• follicle-stimulating hormone (FSH)
• luteinizing hormone (LH)

Question 2

list the anterior pituitary cells as defined by the hormones they produce and where they are located, and what they target

Answer 2

pars distalis:
- thyrotropes: TSH = thyroid T3/T4
- corticotropes: ACTH = adrenal cortex cortisol
- gonadotropes: FSH and LH = gonads sex steroids
- somatotropes: GH = liver tissues etc. IGFs
- lactotropes: PRL = mammary gland milk

pars intermedia (single cell type)
- melanotropes: MSH

Question 3

somatotropes and lactotropes stain

Answer 3

red

Question 4

corticotropes, thyrotropes and gonadotropes stain

Answer 4

blue

Question 5

which hormones regulate somatotropin secretion

Answer 5

• GH releasing hormone
• somatostatin
• ghrelin

Question 6

what do growth hormones do

Answer 6

• stimulates IGF-1 secretion from liver
• growth
• stimulates protein synthesis
• stimulates lipolysis
• inhibits glucose utilization

Question 7

explain why lactotropes stain differently and when

Answer 7

• stain when they are storing PRL in the cytoplasm
• stain poorly when PRL is released

Question 8

what regulates lactotropes

Answer 8

• tonic inhibition by dopamine
• can be stimulated by TRH
• hypertrophy during pregnancy in preparation for lactation

Question 9

what do coticotropes do

Answer 9

• produce the POMC prohormone: proopiomelanocortin
• proteolytic hormones cleave POMC into ACTH, MSH, etc

Question 10

what are corticotropes regulated by

Answer 10

• corticotropin releasing hormone
• tonic stimulation (more CRH increases ACTH secretion, less CRH decreases ACTH secretion)
• negative feedback loop

Question 11

what does FSH do

Answer 11

females: follicle development (ovary) and estradiol (an estrogen) production
male: support spermatogenesis by sertoli cells

Question 12

what do luteinizing hormones

Answer 12

female: stimulates ovulation, corpus luteum development and progesterone
male: maintenance of leydig cells and therefore testosterone production

Question 13

what are gonadotropes regulated by

Answer 13

• GnRH form hypothalamus
• negative feedback loop

Question 14

what do thyrotropes do

Answer 14

• synthesize TSH
• acts on follicular cells of the thyroid gland (produces thyroglobulin that will become triiodothyronine and thyroxine

Question 15

what are thyrotropes regulated by

Answer 15

• thyrotropin-releasing hormone (TRH) from the hypothalamus
• tonic stimulation

Question 16

describe the pars intermedia

Answer 16

• series of small cystic cavaties
• follicles filled with colloid
• residual lumen of rathke pouch
• cells: basophils and chromophobes
• extends into the pars nervosa
• referred to as melanotropes in horses

Question 17

what is a closed feedback loop

Answer 17

• target cells secrete hormones that affect their own secretion
• feedback regulation (usually negative)

Question 18

what is an open feedback loop

Answer 18

• no direct feedback
• stopped by removal of stimulus or depletion of biochemicals
• example: stimulation of milk letdown

Question 19

what is a positive feedback loop

Answer 19

rare
- when secretion of a hormone increases in response to feedback from the organ
- an amplification process

Question 20

what is a negative feedback loop

Answer 20

• the most common type of feedback
• short feedback loop vs long feedback loop

Question 21

describe pituitary dwarfism

Answer 21

• most common in GSD
• caused by cyst in place of the anterior pituitary gland
• lower GH = small dog
• lower ACTH = hypoadrenocoticism
• lower TSH = hypothyroidism
• most die as stillborns, some live to 4/5
• hormone supplementation limited due to species specificity