export_endocrine 3 Flashcards
3 things that happen in growth
1) increase amount of cells
2) increase size of some cells
3) inc bone length and thickness
what hormones promote growth?
- GH (postnatal)
- insulin (fetal)
- TH (permissive)
- testosterone/estrogen (puberty)
effects of cortisol on growth
inhibits
where is GH secreted from?
anterior pituitary
what controls release of GH?
inc GHRH and dec somatostatin (hypothalamus)
effects of GH
- inc cell size
- in cell number
- stim glycolysis and dec glucose uptake to adipos and skeletal
- liver secret higher levels of IGF1 –> inc blood glucose
> cartilage growth
> bone and tissue growth
IGF act as ___ and ___
hormone and paracrine
what increased GHRH secretion?
exercise, stress, fasting, low plasma glucose, sleep
what are negative feedbacks on GHRH secretion?
- plasma GH
- plasma IGF-1 (and neg on GH release)
disorders from GH levels
- dwarfism (deficiency in childhood)
- gigantism (over-secretion in child)
-acromegaly (oversec as adult)
laron dwarfism
abnormal GH receptor - IGF1 not secreted
GH used as therapy for
-adults with pituitary disease
GH in elderly
- inc muscle mass, dec fat
- inc cancer risk bc of prolif cells
what drives bone growth?
- GH and local IGF1
- thyroid hormones and sex hormones
when does bone growth stop?
when osteoblasts overtake condroblasts
what is Ca bound to?
albumin (40%)
phosphate/citrate (10%)
what does Ca mediate?
- parathyroid gland (PTH)
- kidney (vitD)
- bone
- parafollicular C cells (calcitonin)
vitamin D
promotes absorption of Ca from gut
PTH
- produced by parathyroid
- responds to low Ca
-stim kidney to hydroxylate vit D
–> reabsorb Ca and excrete PO4
-osteoclastic resorption of bone (breakdown bone)
how does Ca control PTH?
Ca binds to receptor –> inhibits PTH secretion
how does PTH inc osteoblast activity?
- INDIRECTLY through paracine factor
- talks to osteoblasts
-clasts secrets acid around cell to allow Ca to flow into blood
calcitonin
- produced by thryroid
- inhibts osteoclast resorption of bone
- inc renal Ca excretion
- non essential
- treats osteoporosis
vit D sources
- food
- UV light
-liver then kidney activate
fxn of vit D
- stim osteoblasts
- inc GI absorption of Ca
too much vit D problems?
high levels of Ca in blood
osteoporosis
- low bone mass
- bone resorption>depostion
- estrogen therapy –> stim breast cancer?
- bisphosphonates- kill osteoclasts (not good remodeling)
fxns of TH
- required to synth GH
- permissive for GH actions
how does insulin play into growth?
permissive for GH actions
what do glucocorticoids do?
inhibit growth
what controls thyroid gland?
hypothalamus (TRH)–> pituitary (TSH) –> thyroid (T4/T3)
what is the active form of TH?
T3
how is T4 turned into T3?
deiodination
how is T3 used?
- T3 binds to receptor in nucleus
- inc/dec transcription of genes
-inc mitochondria activity
what does T3 regulate?
- GH
- K/Na ATPase
- lipogenic genes
- uncoupling proteins
- inc breakdown of carbs, lipids
- determines metabolic rate and heat production
T3 effects on other organs
- heart: inc rate, dec force
- vascular: dilation
- GI: inc motility and absorption
- skeletal: inc bone turnover
- neuromusc: hyperactive, inc muscle contraction
endemic cretinism
- lack of I
- low TH level
-little/no growth
goiter
-enlarged thyroid gland
- inc TSH
- inc uptake of I
-gland overgrowth
hasimoto’s
- most common cause of hypothyroidism
- inc TSH
- low TH
- treat with T4
grave’s disease
- auto-antibodies bind to TSH receptor and stim thyroid
- hyperactive thyroid
- low TSH
- inc TH
- inc heart rate and BMR
- inc glycoamino glycan production in the eyes
cortisol secretion
- inc at night
- stress –> hypothal CRH –> pituitary ACTH –> adrenal cortisol
-negative feedback loop to CRH and ACTH
effects of cortisol
- supress immune fxn
- inc gluconeogenesis on liver
- inc protein catabolism
- inc bone breakdown
- inc lipolysis of adipose
why is cortisol high with stress?
- mobilize energy stores
- inc binding of epinephrine to receptors
-allows for cardio health during blood loss
cushing’s syndrome
- inc cortisol secretion
- hyperglycemia
- diabetes
- hypertension
- protein depletion
- altered cognition
- hyperphagia (fat to stomach and shoulders)
- inc ACTH (bronze skin)
addison’s disease
- dec cortisol secretion
- hypoglycemia
- poor stress tolerance
- dec appetite
- bronzing skin
- inc ACTH
