endocrine Flashcards
anterior pituitary: origin, divisions
- originates from primitive oral cavity
- aka adenohypophysis
- pars distalis, pars intermedia, pars tuberalis
somatotropic cells
- acidophils in pars distalis
- secrete GH, target liver (hepatocytes secrete IGF-1
mammotropic, lactotropic cells
- acidophils in pars distalis
- secrete PRL, target mammary gland for mammogenesis, lactation, galactopoeisis
corticotropic cells
- basophils in pars distalis
- secrete ACTH, targets adrenal cortex
thyrotropic cells
- basophils in pars distalis
- secrete TSH, target thyroid for T3, T4 production
gonadotropic cells
- basophils in pars distalis
- secrete FSH, LH, target gonads
pars tuberalis
- extension of pars distalis around infundibular stalk
- more basophils than distalis
pars intermedia
- part of anterior pituitary
- surrounded by cells that secrete melanocyte stimulating hormone
infundibulum
- part of posterior pituitary
- unmyelinated axons originate from supraopitc, paraventricular nuclei
- axons travel hypothalamic-hypophyseal tract, terminate in pars nervosa
hypothalamo-hypophyseal portal system
- neuroendocrine cells in hypothalamic-hypophysiotropic nuclei secrete hormones into primary capillary plexus
- hypophyseal portal vein drains primary plexus into secondary plexus in anterior pituitary
- hormones leave capillaries, inhibit or stimulate chromophils
posterior pituitary: origin, divisions
- upgrowth from hypothalamus
- aka neurohypophpysis
- infundibulum, pars nervosa
pars nervosa
- part of posterior pituitary
- contains axon terminals
- herring bodies store oxytocin, ADH
oxytocin
- from herring bodies in posterior pituitary
- targets myoepithelium of lactating mammary gland, smooth muscle of uterus
ADH
- from herring bodies of posterior pituitary
- targets kidneys, smooth muscle of arterioles
pituicytes
regulate pituitary hormone release
corpora arenacea
- brain sand
- in pineal gland
- contains calcium phosphate, calcium carbonate
pineal gland: secretions
melatonin
- targets hypothalamus, anterior pituitary
- induces sleepiness, inhibits GH and gonadotropin
pinealocytes structure
- spherical nuclei, prominent nucleoli and organelles, secretory granules
thyroid follicular cells
- surround colloid
- store inactive, iodinated thyroglobulin
- release T3, T4
parafollicular (C) cells
- between thyroid follicles
- secrete calcitonin
parathyroid chief cells
- secrete PTH in response to low blood calcium
parathyroid: oxyphil cells
- nonfunctioning: transitioning chief cells
zona glomerulosa
- part of adrenal cortex
- columnar cells
zona fasciculata
- part of adrenal cortex
- cuboidal cells w/ vacuolated cytoplasm cortisol
- targets liver, skeletal muscle, CT, adipose
zona reticularis
- part of adrenal cortex
- irregular cords, secrete weak androgens
chromaffin cells
- in adrenal medulla
- secrete epi/norepinephrine
peptide hormone synthesis
- preprohormone –> prohormone
- prohormone –> hormone
- hormone stored in secretory vesicles
- hormone exocytosed
amino acid derivative hormones: surface receptor type
- dopamine, epinephrine, serotonin
- bind surface receptors, couple to intracellular signaling –> changes in phosphorylation
amino acid derivatives: cytoplasmic receptor type
- T3, T4
- bind cytoplasmic/nuclear receptors, alter gene expression
steroid hormones
- aldosterone, estradiol, cortisol
- bind cytoplasmic/nuclear receptors, alter gene expression
- cholesterol –> pregnenolone –> all other steroids
growth hormone: short term actions
- increased lipolysis, gluconeogenesis
- decreases muscle glucose uptake, prevents cells from using glucose
- anti-insulin/diabetogenic
GH actions: long term
- insulin: permissive effect
- growth via IGF-1, promotes growth
GH: regulation
stimulated by:
- GHRH from hypothalamus
- exercise, fasting, ghrelin, hypoglycemia
inhibited by:
- somatostatin
- hyperglycemia, IGF-1
IGF-1: origin, actions
- from liver in response to GH
- increases AA uptake, cell growth + proliferation, cartilage + bone growth
GH deficiency
- dwarfism in children
- adult GH deficiency
GH excess
- gigantism in children: excess growth before closure of epiphyseal plates
- acromegaly in adults: lateral growth, enlarged hands, feet, coarse facial features
T3, T4 synthesis
Derived from 2 iodinated tyrosines
- iodide enters follicular cell via Na+/I- cotransporter (iodide trapping)
- thyroglobulin synthesized in follicular cells
- in colloid: TPO oxidizes iodide to iodine, iodinates tyrosine (organification)
- couples adjacent tyrosine residues to form thyroid hormones
T3, T4 actions
- opposite metabolic processes occur at once: increases metabolic rate, uses as much energy as possible
- maintains normal growth, devel, increases CO and systolic BP
- decreases TPR –> decreases diastolic BP
T3, T4: regulation
- TSH binding by TSH receptor stimulated iodide trapping, proteolysis, colloid endocytosis
- T3, T4 negatively feeds back on TRH, TSH
hyperthyroidism
Graves’ disease
- autoab acts as TSH agonist
- high T3, T4, low TSH, TRH
- bulging eyes, excess soft tissue growth, bounding pulse
hypothyroidism in childhood
iodide deficiency
- can become irreversible
- delayed development, intellectual disability, protruding abdomen, coarse facial features
hypothyroidism in adults
Hashimoto’s thyroidiitis
- destruction of thyroid cells by autoab
