Endocrine revision (Yr2) Flashcards
what are the endogenous thyroid hormones produced from the thyroid follicle?
triiodothyronine (T3)
thyroxine (T4)
what two hormones regulate thyroid hormone secretion?
thyrotropin releasing hormone (TRH)
thyroid stimulating hormone (TSH)
(influenced by plasma iodide)
what is the metabolically active thyroid hormone?
T4
what are the main actions of thyroid hormones?
stimulate metabolism… increase fat, protein and carbohydrate metabolism, increased oxygen consumption and heat production, increased HR (arrhythmias)
effects growth/development… important for normal skeletal growth, nervous system maturation, promotion of milk production
how does the parasympathetic nervous system effect insulin release?
increased parasympathetic drive increases insulin production (increased sympathetic drive decreases production)
which cells are responsible for which hormones in the pancreas?
beta cells - insulin
alpha cells - glucagon
delta cells - somatostatin
what is the main action of insulin?
facilitate uptake/storage of glucose, amino acids and fats after a meal to reduce blood glucose concentration
what effects does insulin have on the liver?
inhibits glycogenolysis and gluconeogenesis
what effect does insulin have on muscles?
upregulates transport of glucose into cells to stimulate glycogen synthesis
what stimulates glucagon production?
low glucose and fatty acid concentration
high amino acids (high protein meal)
both parasympathetic and sympathetic nervous systems stimulate release
what are the main effects of glucagon?
increases blood glucose
causes fat and protein metabolism
increase HR/contractility (this is less of an effect than the metabolic functions)
what are the three regulating factors of calcium and phosphate homeostasis?
parathyroid hormone
vitamin D (calcitriol)
calcitonin
how does vitamin D effect calcium concentration?
increases absorption of calcium from the gut
how does calitriol and parathyroid hormone contribute to calcium homeostasis?
both enhance calcium absorption from the renal tubules to reduce urinary excretion
what regulate phosphate absorption?
calcitriol
what effect does parathyroid hormone have on phosphate?
mobilise phosphate from bone
inhibits reabsorption (increases excretion) from kidney
what is the main factor controlling parathyroid hormone secretion?
concentration of ionised calcium in blood (low calcium stimulates PTH release)
other than calcium, what will promote parathyroid hormone secretion?
hyperphosphataemia (often an issue with kidney disease as phosphate excretion is impaired)
what is the net effect of parathyroid hormone on calcium and phosphate?
calcium increases and phosphate decreases
what are the main functions of vitamin D (calcitriol) on calcium homeostasis?
increase absorption from gut
mobilise calcium from bone
decrease secretion from kidney (increase reabsorption)
where is calcitonin produced?
thyroid (C cells)
what drives calcitonin secretion?
hypercalcaemia
what is the main action of calcitonin?
decrease bone reabsorption (also decrease calcium and phosphate reabsorption from the kidney)
how do glucocorticoids effect calcium homeostasis?
higher concentrations inhibit bone formation by inhibiting osteoblast differentiation
what stimulates the release of glucocorticoids?
ACTH from the anterior pituitary gland
what regulates ACTH release?
corticotropin releasing hormone
what are the main metabolic effects of glucocorticoids?
mainly carbohydrate and protein metabolism…
decreased uptake/utilisation of glucose and increased glycogen storage (can result in hyperglycaemia)
decreased protein synthesis and increase breakdown (leads to muscle wasting)
chronic increases can cause redistribution of fat (sign of cushings)
decrease calcium absorption (can lead to osteoporosis)
what can very high levels of glucocorticoids cause? (usually pharmacological than physiological)
sodium ion retention and potassium ion loss (mineralocorticoid action)
what are glucocorticoids commonly used for in veterinary medicine?
immune-suppression and anti-inflammatory
what is the main endogenous mineralocorticoid?
aldosterone
what is aldosterone release/synthesis regulated by?
plasma electrolyte composition
angiotensin II system
what are the two main factors that cause aldosterone release?
high plasma potassium concentration
RAAS
