Endocrinology Lecture 2 Flashcards
The thyroid gland structure and what hormone types it produces
Two lateral lobes joined by the isthmus in the middle
Produces two types of hormones:
Thyroid hormone: T3/T4
Calcitonin: involved with calcium and phosphorus metabolism
T3 and T4 facts
T4 more produced but T3 is 3x more potent
T4 considered a pro hormone as it can be turned to T3 in peripheral tissues
Thyroid hormones regulate gene expression
T3 deficiency hypothyroidism
What is a prohormone
A prohormone is a precursor of a hormone
Circulates in blood as a hormone inactive switched on by post translational modification
T4 becomes T3 by removing an iodine via deiodinase
Thyroid can build a 6 month supply of hormones but stability issue
T3 half life is one day
T4 is 5 times more stable but still short
Synthesis of hormones on demand requires iodide which isn’t always available
Proteolysis T3 and T4 from larger molecule
Why is T3/4 hard to store?
They are hydrophobic
Solution is to synthesise T3 and T4 from a larger hydrophilic protein
What do T3/4 do?
Key regulator of metabolism via gene regulation
Direct and indirect effects:
Increase BMR and oxygen consumption and lipid synthesis/lysis
Insulin and cathecolamine increase
What does calcitonin do
Lowers calcium release in osteoclasts in bone
Increases kidney calcium
Usually thyroid release goes to pituitary gland releasing TSH from pituitary
TSH stops thyroid hormone release
What is Graves’ disease
Autoimmune condition that sends antibodies against TSH receptors and some of these antibodies mimic TSH action
Cellular changes in gland as more follicular cells produced in thyroid making it big and also lead to eye bulging
What are parathyroid glands?
Four on the posterior surface of the thyroid
Two types of cells:
Chief cells produced PTH and they surround the capillaries and are often inactive
Oxyophil cells: function is unknown
What is the function of PTH
Opposite of calcitonin as it reduced calcium when it’s too high in the blood via:
Stimulating osteoclasts to release calcium
Decreases kidney excretion of calcium and activates vitamin d to take up calcium in instestines
Pituitary gland where is it found
Pea sized gland underneath the brain and behind bridge of the nose
(Hypophysis)
Anterior pitusrity known as adenohypophysis
Posterior attached to hypothalamus which controls it
What does pituitary gland do?
Known as the master gland it controls many processes like:
Blood pressure
Sexual maturation and reproduction
Metabolism
Growth
What does anterior pituitary gland do?
Makes and secretes hormones
Non nerve embryonic origin
Hypophyseal portal system carries blood from hypothalamus to anterior then to posterior
What does posterior pituitary gland do
Nervous embryonic origin stored and secreted hormones and makes hypothalamic neurons (Neurohormones)
What is the main brain of the endocrine system?
The hypothalamus as it receives info from the cortex thalamus and limbic system
What are the 8 hormones released by pituitary gland
TSH
ACTH
FSH
LH
GH
PRL
(Posterior secretes 2)
ADH
oxytocin
What does ACTH TSH FSH LH do?
ACTH tells adrenal gland to release corticosteroids for stress
TSH for thyroid hormones in metabolism
FSH for oestrogen production and follicle growth, Sperm production in males
LH plays a role in ovulation and stimulates androgen in testes
Prolactin for breast growth and milk production
ADH and oxytocin
ADH for water retention and vessel constriction
Oxytocin for childbirth contractions breast milk and social bonding
How is pituitary gland regulated
Hypothalamus release RH to stimulate synth/secretion of hormones at the anterior pituitary gland (RH is always releasing hormones)
IH is inhibiting hormone
If pituitary gland doesn’t work due to tumour or dysfunction wha happens
Andre the giant excess GH
Or under GH secretion midget and shit
Adrenal gland structure aka surreal glands
Adrenal cortex outer layers and adrenal medulla inner layer
What does the cortex and medulla secrete
Cortex- secretes lipid steroid hormones like corticosteroids, aldosterone and cortisol
Medulla- secretes adrenaline and noradrenaline via chromaffin cells
What does the mineralocorticoid aldosterone do
Responded to decline in blood volume or pressure
Prompts distal and collecting tubules to reabsorb more sodium
