Hormone Functions

Question 1

Growth Hormone - Functions

Answer 1

• Lipolysis in adipose tissue
• Gluconeogenesis and glycogenolysis in liver
• Insulin resistance in tissue (increases blood glucose)
• Stimulates release of IGF-1 (somatomedins act as negative feedback via somatostatin release)

Question 2

IGF-1 - Functions

Answer 2

• Skeletal muscle - increases amino acid uptake = muscle growth
• Long bones: increases osteoblast and chondrocyte activity
• Act as negative feedback via somatostatin release

Question 3

Stimulates GH secretion

Answer 3

• GHRH
• Hypoglycemia
• Exercise/epinephrine release
• Estrogen/testosterone (ex: puberty)
• Deep sleep

Question 4

Somatostatin

Answer 4

• Also called GHIH
• Inhibits GHRH release
• Inhibits insulin/glucagon/gastrin/VIP release frmo pancreas

Question 5

Inhibits GH secretion

Answer 5

• Negative feedback (increased [GH])
• Somatomedins (IGF)
• Somatostatin (GHIH)

Question 6

Glucagon Functions

Answer 6

Liver: Glycogenolysis and gluconeogenesis
Adipose: Lipolysis

• Causes small rise in insulin to allow cells to take in newly formed glucose

Question 7

Stimulates glucagon release

Answer 7

• Hypoglycemia/Fasting
• Amino acids
• Epi/NE/Cortisol
• Exercise

Question 8

Inhibits glucagon release

Answer 8

• Incretins (GIP/GLP)
• GH
• Hyperglycemia/
• Insulin
• Somatostatin

Question 9

Pregnancy effects on thyroid hormone system

Answer 9

Increased estrogen increases TBG. Because of this, a pregnant woman with hypothyroidism can appear to have normal T4 levels while having low TSH.

Question 10

Hypoglycemia causes what changes in hormones?

Answer 10

• Increased GH
• Increased epi
• Increased cortisol
• Increased glucagon

Question 11

Stimulates cortisol release

Answer 11

• ACTH
• Stress
• Infxn
• Hypoglycemia

Question 12

Cortisol Functions

Answer 12

Immune effects:
- Inhibit inflammatory process (via inhibition of prostaglandins and leukotrienes)

Metabolic effects:

• Adipose tissue: lipolysis
• Skeletal muscle: proteolysis
• Increases insulin resistance
• Stimulates insulin release
• Liver: gluconeogenesis
• Inhibits osteoblasts
• Inhibits fibroblasts

Question 13

ACTH Functions

Answer 13

• Stimulate release of glucocorticoids
• Less stimulation of mineralcorticoids (majorly regulated by RAAS)
• Triggers melanocytes –> hyperpigmentation
• Negative feedback

Question 14

PTH functions

Answer 14

• Increases Ca++ by:
  
  • Increasing osteoclast activity
  • Increases Ca++ reabsorption in kidneys
  • Decrease phosphate reabsorption in kidneys
  • Increases synthesis of active vitamin D via 1-a-hydroxylase
    
    • Active vitamin D increases intestinal Ca++ absorption

Question 15

Inhibits PTH release

Answer 15

• Increased Ca++
• Increased calcitriol
• Increased FGF-23 activity in osteocytes

Question 16

Stimulates PTH release

Answer 16

• Increased Pi

- Low Ca++

Question 17

FGF-23 Functions

Answer 17

• Inhibits PTH system
• Inhibits 1-2-hydroxylase (vit D activation)
• Inhibits Pi reabsorption in kidneys

Question 18

Stimulates FGF-23 release

Answer 18

• Increased Pi
• High PTH
• High calcitriol

Question 19

Stimulates Insulin Release

Answer 19

• Hyperglycemia
• Incretins (GIP/GLP)
• Amino acids
• Glucagon
• Sulfonylureas

Question 20

Phosphorylation of IRS-1 in insulin resistance

Answer 20

Excess glucose is oxidized
Creates oxidative stress –> Activation of stress kinase JNK –>

Serine phosphorylation

= decreased PI-3 kinase/Akt pathway activation –> less translocation of GLUT 4 vesicles

Question 21

Phosphorylation of IRS-1 in insulin sensitivity

Answer 21

Tyrosine phosphorylation –>PI-3 kinase –> Akt Pathway –> translocation of GLUT 4 vesicles