endocrinology of growth Flashcards
BBB
specialized endothelium with tight junctions to strictly control enviromental exposure and protect the brain
where is the BBB lacking
regions where hormones are intended for entry to the circulation such as the hypothalamic-hypophyseal portal system
regions where the neurons need to respond to stimuli from circulation such as osmolarity detetetion, vomiting centre
what in the anterior pituitary is programmed to secrete different trophic hormones
cells - tropes
how many and what are the 5 different cell populations within the anterior pituitary
5, they are
-somatotropes/somatotrophs; produce GH
-lacrotropes- produce prolactin
-tyrotropes- produce TSH- thyroid stimulating hormone
-gonadotropes- produce LH or FSH- leteinizing hormone or follicle stimulating hormone
cotricotropes- produce ACTH- adrenocorticotrophic hormone
what does the hormonal output of the anterior pituitary represent
a more complex endocrine negative feedback loop
what is the secretion of all anterior pituitary hormones controlled by
hypothalamic hormones
what is the special portal system
vascular network called the hypothalamic-hypophyseal portal system
hypophysis meaning
pituitary
what is hormone 1 of the loop
hypothalamic releasing hormones or hypothalamic inhibiting hormones
what do hypothalamic releasing hormones do
stimulate release of a specific hormone from the cells of the anterior pituitary that express the releasing hormone receptor
what are the hypothalamic releasing hormones
-thyrotropin releasing hormone TRH
-cotricotropin releasing hormone CRH
-growth hormone releasing hormone GHRH
-prolactin releasing hormone PRH
-gonadotropin releasing hormone GNRH
what are two examples of hypothalamic inhibiting hormones
prolactin inhibitory hormone PIH/ dopamine
growth hormone inhibitory hormone GHIH
what is dopamine
a neurotransmitter in the brain as well as prolactin inhibitory hormone
what cells secrete anterior pituitary hormones into systemic blood
endocrine cells of anterior pituitary
what secretes releasing and inhibiting hormones into portal system
neurosecretory neurons in hypothalamus
what inacts negative feedback on the hypothalamus and the anterior pituitary
hormone 3
what hormones exhibit circadian/ dinural rhythms. what does this arise from
hypothalamic releasing hormones, their anterior pituitary hormones and their target cell hormones
this arises from intrinsic neural oscillators
what is an exception to the dinural circadian rythm produced by the three hormones of the anterior pituitary loop
prolactin. its role in lactation does not need it to be dinural like that
how many and when are the peaks of circadian rhythm of secretion
1 major peak every 24 hrs
how many and when are the peaks of circadian rhythm of secretion
1 major peak every 24 hrs
each anterior pituitary hormones peaks at a different time and the endocrine activity of the target organs reflects this oscillation
what kind of molecule is cotrisol
a steroid
how much cortisol is there when we are awake compared to sleeping
low when asleep, high when awake
what are the 3 families of hormone 2 of the feedback loop in the anterior pituitary
- glycoprotein family
- POMC- pro-opiomelanocortin family
- GH/ prolactin family
glycoprotein family facts
hydrophilic
produced and stored in anterior pituitary cells- gonadotropes or thyrotropes
what are the glycoprotein horomones
FSH- folicle stimulating hormone
LH- lutenizing hormone
both together are called gonadotropins
TSH- thyroid stimulating hormone
what do gonadotropins FSH and LH act on
gonadal target cells
-stimulate folicle development and secretion of estrogen and progesterone by ovaries
-stimulate spermatogenesis and secretion of androgens in testes
what cells do TSH hormones act on
thyroid gland cells to stimulate secretion of thyroid hormones
what is POMC glycoprotien pro hormone cleaved into and where is it cleaved
cleaved in corticotropes and cleaved into
ACTH- adrenocorticotropic hormone
beta- endorphin
Gamma lipotropin
what stimulates production of POMC
CRH- corticotropin releasing hormone from the hypothalamus by corticotropes of the anterior pituitary
MSH
MELANOCYTE STIMULATING HORMONE
What does ACTH do
targets cells in adrenal gland cortex
controls or modulates secretion of adrenal cotrical hormones such as
-aldosterone
-cortisol
-androgens
what is the structure of growth hormones prolactin family
GH and prolactin are proteins somewhat structurally related
what does prolacin do
stiumlates milk production in lactating women
additional roles for prolactin include fertility regulation in men and women and maintenance of immune system
what are some activities of GH
metabolism and growth
-increased lipolysis
-increased protein synthesis
-increased use of fatty acids
-increased collagen synthesis
-decreased glycogen synthesis
-increased cartilage growth
-reduced glucose use
-promotion of hypertrophy and hyperpalasia in tissues
what is the zone for bone growth
epiphyseal plate
what type of growers are humans
detemrinate growers but snakes and sharks are indeterminate growers
long bone growth plate
-chondrocytes undergo cell division
-older chondrocytes enlarge
-calcification of extracellular matrix entraps chondrocytes and they die
-dead chondrocytes are cleared away by osteoclasts
-osteoblasts swim up from diaphysis and deposit bone over persisting remnants of disintegrated carilage
how is hieght calculated
M+F/2
men add 2.5 inches and owmen subtract 1.5 inches
IGF1
Insulin like growth factor 1
what is the net secretion of GH from anterior pituitary gland regulated by
stiumlatory and inhibitory inputs
metabolic actions of GH growth hormone
acute metabolic effects- diabetogenic actions
what are the growth actions of GH
long term growth effects via IGF1
What is secretion of GH stimulated by
stress
exercise
What is secretion of GH stimulated by
stress
exercise
hypoglycemia, fasting
some amino acids especially arginine and leucine
first two hours of deep sleep
gigantism
abnormally large growth due to an excess of GH during childhood before bone growth epiphyseal plates have closed
acromegaly
occurs when GH is secreted after epiphyseal plates are closed
height is unchanged but mature bones become thicker in the face, hands, and feet therefor we have an increased coarseness of features
treatment of short stature in femails 4 11 and males 5 4 by age 18
recombinant GH if requested
what is an example of short stature
turners syndrome- one of the x chromosomes is missing or partially misssing in females
they have short stature
GH recomended at puberty
pituitary dwarfism
GHRH, GH, or IGF1 deficiency
laron dwarfism
unresponsive GH receptors
cretisism
hypothyroidism
-thyroid hormones are permissive for action of GH
-poor long bone growth as a result of thyroid hormone insufficiency
cretisism
hypothyroidism
-thyroid hormones are permissive for action of GH
-poor long bone growth as a result of thyroid hormone insufficiency
cretisism
hypothyroidism
-thyroid hormones are permissive for action of GH
-poor long bone growth as a result of thyroid hormone insufficiency
what impairs bone ossification
gene defect for cartilage FGF fibroblast growth factor receptor
what is achondrophlasia
impaired bone ossification
