Hormone Functions Flashcards
Growth Hormone - Functions
- 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)
IGF-1 - Functions
- Skeletal muscle - increases amino acid uptake = muscle growth
- Long bones: increases osteoblast and chondrocyte activity
- Act as negative feedback via somatostatin release
Stimulates GH secretion
- GHRH
- Hypoglycemia
- Exercise/epinephrine release
- Estrogen/testosterone (ex: puberty)
- Deep sleep
Somatostatin
- Also called GHIH
- Inhibits GHRH release
- Inhibits insulin/glucagon/gastrin/VIP release frmo pancreas
Inhibits GH secretion
- Negative feedback (increased [GH])
- Somatomedins (IGF)
- Somatostatin (GHIH)
Glucagon Functions
Liver: Glycogenolysis and gluconeogenesis
Adipose: Lipolysis
- Causes small rise in insulin to allow cells to take in newly formed glucose
Stimulates glucagon release
- Hypoglycemia/Fasting
- Amino acids
- Epi/NE/Cortisol
- Exercise
Inhibits glucagon release
- Incretins (GIP/GLP)
- GH
- Hyperglycemia/
- Insulin
- Somatostatin
Pregnancy effects on thyroid hormone system
Increased estrogen increases TBG. Because of this, a pregnant woman with hypothyroidism can appear to have normal T4 levels while having low TSH.
Hypoglycemia causes what changes in hormones?
- Increased GH
- Increased epi
- Increased cortisol
- Increased glucagon
Stimulates cortisol release
- ACTH
- Stress
- Infxn
- Hypoglycemia
Cortisol Functions
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
ACTH Functions
- Stimulate release of glucocorticoids
- Less stimulation of mineralcorticoids (majorly regulated by RAAS)
- Triggers melanocytes –> hyperpigmentation
- Negative feedback
PTH functions
- 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
Inhibits PTH release
- Increased Ca++
- Increased calcitriol
- Increased FGF-23 activity in osteocytes
Stimulates PTH release
- Increased Pi
- Low Ca++
FGF-23 Functions
- Inhibits PTH system
- Inhibits 1-2-hydroxylase (vit D activation)
- Inhibits Pi reabsorption in kidneys
Stimulates FGF-23 release
- Increased Pi
- High PTH
- High calcitriol
Stimulates Insulin Release
- Hyperglycemia
- Incretins (GIP/GLP)
- Amino acids
- Glucagon
- Sulfonylureas
Phosphorylation of IRS-1 in insulin resistance
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
Phosphorylation of IRS-1 in insulin sensitivity
Tyrosine phosphorylation –>PI-3 kinase –> Akt Pathway –> translocation of GLUT 4 vesicles
