Anterior lobe histologic regions and their secretions?
Pars distalis- pituitary hormones
Pars intermedia- secretes MSH
Posterior lobe histology:
Pars nervosa (because posterior lobe is part of the nervous tissue)
What is the major product of POMC gene cleavage?
ACTH
(MSH is the other thing)
Corticotrope is the _______ found in ________, and it secretes ______ in the anterior pituitary
Pituitary cell
Anterior pituitary
Corticotropin= ACTH
What is the hypothalamic hormone that stimulates corticotropes?
CRH (corticotropin-releasing hormone)
What is the hypothalamic hormone that stimulates the thyrotropes? What inhibits it?
Thyrotropin-releasing hormone
Somatostatin inhibits it
What is the hypothalamic hormone that stimulates gonadotropes? What is the hormone secreted from the anterior pituitary as a result?
GnRH (gonadotropin-releasing hormone)
LH and FSH released from anterior pituitary
What is the hypothalamic hormone that stimulates somatotropes? What inhibits it?
GHRH (growth hormone releasing hormone)
Somatostatin inhibits it
What is the hypothalamic hormone that stimulates lactotropes?
Prolactin inhibiting hormone = dopamine
Growth hormone is aka _____, secreted by the ______ that is stimulated by the hypothalamic hormone _____
Somatotropin
Anterior pituitary hormone
Growth hormone releasing hormone
Thyrotropin is aka ______, which is secreted by the _____ stimulated by the hypothalamic hormone _____
Thyroid stimulating hormone
Anterior pituitary
Thyrotropin-releasing hormone
What are the two inhibitory hypothalamic releasing hormones?
Prolactin inhibitor factor
Somatostatin
T/F: for prolactin, the prolactin releasing hormone is secreted from the hypothalamus that tells the breast to stimulate prolactin
False; there is no specific hypothalamic releasing hormone for PRL, but TRH (thyrotropin releasing hormone) and GnRH (gonadotropin releasing hormone) increases PRL release
Examples of positive feedback loops:
Ferguson reflex – more oxytocin to increase uterine contraction
Lactation
Blood clotting
What is the ferguson reflex and this is an example of which type of feedback loop?
Ferguson reflex is when more oxytocin is released to increase uterine contraction
It is an example of positive feedback loop
Where is GH stored, made and released from?
Somatotropes in the anterior pituitary
Targets of growth hormone?
Bone, muscle and adipose tissues
Control growth of the body
T/F: GH secretion is pulsatile and more secretion occurs during sleep at night
True
T/F: GH is released following stress, hypoglycemia, and during exercise
True
GHRH, secreted by the _____ neurons in the hypothalamus binds to ______ receptor on the somatotropes and activate ________ to stimulate _______. Subsequent rise in ____ causes increased transcription of GH
Arcuate
G-protein-coupled receptor
Gs
Adenylyl cyclase
cAMP
Does increase in calcium concentration (stimulate/ inhibit) release of pre-formed GH
Stimulate
Somatostatin binds to the ____ receptor on somatotropes and activate ____ which _____ adenylyl cyclase, and leading to _____ concentration of calcium
GPCR (same as GHRH)
Gi (as opposed to Gs for GHRH)
Inhibits (As opposed to stimulate for GHRH)
Decreased calcium which diminishes the responsiveness of GHRH
What triggers the secretion of IGF-1 from GH target tissues
Growth hormones
T/F: both GH and IGF-1 feedback either directly or indirectly on the somatotropes to decrease GH secretion
True
Can GH inhibits GH itself?
Yes it can
What are the three ways that IGF-1 can inhibit GH release?
1 directly inhibit somatotropes
2 indirectly suppress GHRH release in the hypothalamus
3 induces an increase in secretion of somatostatin which inhibits somatotropes
GH has a half-life of _____ minutes
25
Growth hormone receptor is a JAK receptor, what are the intracellular that it can trigger when activated?
STAT (signal transducer and activator of transcription)
IRS (insulin receptor substrate)
PI3K (phosphatidylinositol 3- kinase)
MAPK (mitogen activated protein kinase)
Since GH lacks growth promoting actions itself, what are the two somatomedin peptides that resemble proinsulin and mediate somatic effects of GH?
IGF-1 and IGF-2
What is the function of IGF-1 (and IGF-2)?
Mediate somatic effects of GH as GH does not have growth-promoting actions
So it helps with longitudinal bone growth
What is the major serum carrier protein for IGF-1?
IGFBP-3 made in the liver
T/F: IGF-1 promotes growth of connective tissues and soft tissue thickening
False; IGF-1 promotes longitudinal bone growth on growth plate and increase chondrogenesis and cartilage formation
IGF-1 receptor has two _____alpha chains and 2 _____ beta chains; and it is the ____ chains that have intrinsic ______ kinase activity
Extracellular alpha
Transmembrane beta
Beta
Tyrosine kinase
Increase in GH in the blood would ____ IGFBP (IGF-1 binding protein) and _____ ALS
Increase
Increase
These three present as a complex in circulation
What is the most useful clinical measures of excess GH secretion?
IGF-1 concentration
T/F: serum GH in normal individuals can fluctuate between undetectable levels and peaks
True
What happens with the serum GH level in patients with acromegaly?
GH hypersecretion is continuous and so GH level never returns to undetectable levels like in those of normal individuals
What causes primary adrenal insufficiency?
Adrenal damage, resulting in increased ACTH and increased CRH
What causes secondary adrenal insufficiency?
Pituitary damage, resulting in increase CRH
What causes tertiary adrenal insufficiency?
Hypothalamic damage, resulting in decreased CRH and ACTH
What is acromegaly? Clinical presentation of acromegaly?
GH hypersecretion with variety of bony and soft tissue abnormalities developing
Increase metabolic rate, excessive sweating, increased sebum production
T/F: GH is known to decrease sex hormone-binding globulin, leading to elevated free testosterone level
