Hormone Actions

Question 1

ADH

Answer 1

1. Supraoptic nucleus in hypothalamus –> posterior pituitary. Released w/ low BP or high plasma osmolality.
2. Nephron: distal collecting ducts –> increased aquaporins to increase H2O reabsorption
3. Vasc. sm muscle: inc. Ca++ influx –> contraction –> vasoconstriction + inc. BP
4. Low ADH –> Diabetes insipidus. High ADH –> SIADH (cerebal oedema)

Question 2

Growth Hormone

Answer 2

1. Hypothal –> Growth Hormone Releasing Hormone (stim. by exercise high AAs. low glucose/FAs in blood) –> somatotropes in post. pituitary release GH
2. GH Actions
   a) Liver: gluconeogenesis + release IGF-1
   b) Adipose: lipolysis
   c) Muscles: inc. aa uptake

IGF-1 Actions:
- muscle: inc. aa uptake and protein synth = hypertrophy
- bones: inc. osteoclast/osteoblast action –> endochondral ossification, + inc. proteoglycans and type 1 collagen production
- cartilage: inc. size, prolif, differentiation of chondroblasts –> bone grows in length

Question 3

Thyroid Hormone Synthesis

Answer 3

1. TRH from hypothal
2. TSH from ant.pituitary
3. TSH stims. follicular cells of thyroid glands to produce thyroglobulin
4. Thyroid Peroxidase
   a) Iodide oxidation –> Iodine
   b) Iodination of Tyrosine aas
   c) Coupling –> T3/T4
5. Endocytosis of T3 + T4 –> thyroxine binding globulin –> transportationg around body to effector organs etc.

Question 4

Thyroid Hormone Effects

Answer 4

T4 –> T3 (active form) via 5’Deiodinase
1. Cellular level: increased 3Na/2K ATPase pumps –> increased ATP use/metabolism –> increased heat production and O2 consumption
2. Liver: increased glycogenolysis and gluconeogenesis -> inc. BG. _ LDL uptake.
3. Heart: increased B1-AR expression on AV/SA node to inc. HR and on myocardium to incr. contractility
4. CNS; increased myelination, dendrites and synapses (excitatory), increased SNS sensitivity
5. Bone: usually keeps osteoclast/blast activity balanced, also stimulates endochondral ossiciation and interstitial growth
6. Adipose: incr. lipolysis
7. Muscles; balance of anabolism and catabolism
8. Skin: vasodilation + inc. sweat production
9. GIT: inc. motility and secretions

Question 5

PTH effect on calcium
(from chief cells)

Answer 5

1. Bone: increased osteoclast activity = bone resorption
2. Renal:
   a) DCT: increased calcium reabsorption
   b)1-a-hydroxylase inc. + 25-OHCCF ==>1,25-DHCCF (calcitriol/vit.D)
   2bii) Vit.D acts on duodenal enterocytes to inc. Ca++ absorption in GIT

Question 6

Calcitonin effect

Answer 6

from Parafollicular cells –> stim. by high calcium. Inihibts Osteoclastic activity ==> rel. higher osteoblastic activity and bone deposition
(to lower blood calcium)