Arroyo: Anterior Pituitary

Question 1

Pituitary Gland: Location, functional lobes, portal system

Answer 1

• Located in the brain; size of a pea
• Two functional lobes
  
  • Anterior (adenohypophysis) - glandular tissue
  • Posterior (neurohypophysis) - nervous tissue
• “Master endocrine gland” - affects other glands
• Releases 9 important peptide hormones
• Hormones bind to membrane receptors - use cAMP as second messenger
• Hypothalamo-hypophyseal portal system

Question 2

What is the hypothalamo-hypophyseal portal system?

Answer 2

Hypothalamo-hypophyseal portal system: portal veins that shunt blood carrying regulatory hormones from hypothalamus to the anterior pituitary

• Median eminence
  
  • Swelling near infundibulum attachment
  • Where hypothalamic neurons release regulatory factors into interstitial fluids and through fenestrated capillaries
• Portal vessels
  
  • BV’s linked to two capillary networks
  • Entire complex is portal system
  • Ensures that regulatory factors reach correct target cells before entering general circulation

Question 3

What are the three regions of the anterior pituitary gland?

Answer 3

• Pars distalis
• Pars tuberalis
• Pars intermedia

Question 4

List the anterior pituitary hormones

Answer 4

• FSH - follicle stimulating hormone
• LH - lutenizing hormone
• ACTH - adrenocorticotropic hormone
• TSH - thyroid stimulating hormone
• PRL - prolactin
• GH - growth hormone

Question 5

GH: major target organ(s), effects, deficiency, what can go wrong

Answer 5

• Major target organ(s): Liver, adipose tissue
  
  • ​All cells in the body
• Effects: Indirectly promotes growth; control of protein; lipid and carb metabolism
  
  • ​Stimulates cell growth and division; liver production of somatomedin
• What can go wrong?
  
  • Dwarfism - hyposecretion
  • Gigantism - hypersecretion pre-plate closure
  • Acromegaly - hypersecretion post-plate closure
• Factors affecting GH: Stress, sleeping, exercise, blood glc levels
• Replacement tx for deficiency via recombinant DNA technology

Question 6

TSH: major target organ(s), effects, deficiency, what can go wrong

Answer 6

• Major Target Organ(s): Thyroid gland
• Effects: Stimulates secretion of thyroid hormones
• Deficiency: Metabolism, CV, GI tract, motor nervous system
• What can go wrong? Congenital problems - affecting any of the pituitary, loss of midline structures like septo-optic dysplasia (optic nerve loss)
• Factors affecting release: Blood levels, glucose, metabolic rate

Question 7

ACTH: major target organ(s), effects, deficiency, what can go wrong

Answer 7

• Major Target Organ(s): Adrenal gland cortex
• Effects: Stimulates glucocorticoid production and secretion
• Deficiency: Stress
• What can go wrong: Cushing Syndrome - body tissue exposed to cortisol for long period of time
  
  • Decreased immune response > more prone to infection > decreased resistance to stress > death from infection

Question 8

PRL: major target organ(s), effects, deficiency, what can go wrong

Answer 8

• Major Target Organ(s): Mammary glands
• Effects:
  
  • Females: Mammary gland growth and milk production
  • Males: Influence sensitivity of interstitial cells to LH
• Deficiency: Little or not milk production; infertility
• What can go wrong: High levels = reproductive function loss, inappropriate milk production

Question 9

LH: major target organ(s), effects, deficiency, what can go wrong

Answer 9

• Major Target Organ(s): Ovary and testis
• Effects:
  
  • ​Females: Follicular cells in ovary to regulate ovulation and production of progesterone
  • Males: Interestitial cells in testes to regulate production of testosterone
• Deficiency: Irregular periods; impotence
• What can go wrong: Amenorrhea; impotence

Question 10

FSH: major target organ(s), effects, deficiency, what can go wrong

Answer 10

• Major Target Organ(s): Ovary and testis
• Effects:
  
  • ​Females: Follicular cells in ovaries to regulate maturation of follicular cells and oocytes and production of estrogen
• Deficiency: Irregular menstrual cycle; affected production of sperm; impotence
• What can go wrong: Lack of ovulation; infertility in males