Endocrinology

Question 1

What are the 3 methods of hormone action/homeostasis/movement?

Answer 1

Endocrine - Secretion into the bloodstream, hormones act on cells further away (e.g. ADH from posterior pituitary)

Paracrine - Secretion into ECF, hormones act on adjacent/neighbouring cells (e.g. acetylcholine at the neuromuscular junction)

Autocrine - Feedback on the same cell that secreted the hormone

Question 2

Differences between peptide and steroid hormones

Answer 2

Peptide - made from amino acids
Steroid - made from lipid cholesterol

Peptide - water soluble (move directly in blood) - ADH, insulin
Steroid - lipid soluble (move in transport proteins in the blood) - oestrogen, testosterone

Peptide- bind to receptors on cell membrane
Steroid - diffuse through cell membrane to produce intracellular response

Peptide - fast acting and short half life (fast clearance)
Steroid - short acting and longer half life (slow clearance)

Peptide - premade and stored in secretory granules
Steroid - synthesised on demand

Question 3

3 hormone receptor locations (and name some hormones that bind there)

Answer 3

Cell membrane receptors - peptide hormones e.g. growth hormone, prolactin, insulin

Receptors in the cytoplasm - steroid hormones e.g. glucocorticoids, mineralocorticoids, androgens

Receptors in the nucleus - e.g. oestrogen, thyroid hormone, vitamin D

Question 3

Function of thyroid hormone

Answer 3

• Accelerate food metabolism
• Increase protein synthesis
• Increase ventilation rate
• Increase cardiac output and heart rate
• Accelerate growth rate

Question 3

What does the anterior and posterior pituitary secrete? (where do these hormones act)

Answer 3

Synthesised in the hypothalamus and stored in the posterior pituitary - Vasopressin acts on the DCT and collecting duct. Oxytocin acts on breast and uterus (also other organs)

Posterior pituitary
Thyrotrophs - TSH - Thyroid
Lactotrophs - Prolactin - mammary glands
Somatotrophs - Growth hormone - entire body
Corticotrophs - ACTH - Adrenal cortex
Gonadotrophs - FSH and LH - testes or ovaries.

Question 3

GH axis

Question 4

HPT axis

Question 5

HPA axis

Question 6

Part of adrenal glands and kidneys (reticualaris, fasciculata)
Mineralo corticoids, glucocorticoids

Question 7

HPG axis

Question 8

Hyperprolactinaemia

Question 9

Function of PTH, Calcitriol and Calcitonin

Answer 9

PTH
- Increases resorption of bone by osteoclasts - releasing calcium
- Activates calcitriol (vitamin D) which increases intestinal absorption of calcium
- Increased calcium reabsorption and phosphate excretion in the kidney

Calcitriol (release stimulated by low plasma calcium or phosphate, or PTH)
- Increases calcium intestinal absorption
- Inhibit PTH release - negative feedback
- Increases calcium and phosphate reabsorption in kidney

Calcitonin (made in C cells of thyroid)
- Cause a decrease in plasma calcium and phosphate

Question 10

Is it really hypocalcemia? Is it really hypercalcemia?