Endocrine - Hypothalamus and Pituitary Glands Flashcards
What does the Hypothalamus Secrete?
Dopamine
TRH
CRH
GnRH
GHRH
SS
Where is the hypothalamus?
Above the pituitary gland
Neural Tissue
What is the function of the hypothalamus?
Integrates sensory stimuli about heat, light, and BP, etc.
Communicates with pituitary to direct physiological responses
Releasing hormones secreted into a portal capillary bed stimulate cells the anterior pituitary gland
Define
Supraoptic nuclei (SON) and Paraventricular nuclei (PVN)
What are they? Where are they?
Collections of neurons that project to the posterior pituitary gland (neural communication)
Tumors in the anteror pituitary can cause vision loss due to…
compression of the optic chiasm
What is the function of the Posterior Pituitary Gland?
Extension of the hypothalamus
Hormones synthesized in hypothalamus travel through axons to the posterior pituitary gland
APs stimulate release of hormones from posterior pituitary
What happens once hormone release is stimulated in posterior pituitary?
APs stimulate the release of hormones from the posterior pituitary gland into the vascular capillary bed
Hormones travel through the bloodstream to target organs
Define
Magnocellular
Cell bodies found in the hypothalamus synthesize hormones
What hormones are released from the Posterior Pituitary?
Oxytocin
ADH
What is the function of Oxytocin?
Uterine muscle contraction during birth and contraction of myoepithelial cells in breath
Why is oxytocin released?
Birth - in response to cervical stretch
Suckling of nipple for milk
What is the function of ADH?
Water reabsorption in the kidney to ↑ water in plasma → ↑ BP, ↓water in urine
What kind of feedback loop is the release of oxytocin?
Positive
Why is ADH released?
↓BP
↑Plasma osmolarity
Dehydration
Parvocellular Neurons
In the hypothalamus
Secrete releasing hormones into the hypothalamohypopyseal portal vessels
What is the function of the Anterior Pituitary?
Releasing hormones secreted into the hypothalamohypopyseal portal vessels stimulate anterior pituitary cells to release different tropic hormones into the bloodstream that travel to target organs to stimulate secretion of other hormones
What does the Anterior Pituitary Gland secrete?
FSH
LH
ACTH
TSH
Prolactin
I (Ignore)
GH
FLAT PIG
What needs to happen to hormones released from the anterior pituitary because they are peptide/protein hormones?
They need to bind to receptors located in the cell membrane of target cells
They will also elicit responses quickly in target cells (often stimulating release of hormone containing vesicles)
What is unique about GH and Prolactin?
Both have negative inhibitors
↓ negative regulator → remove inhibition → ↑ prolactin or GH
Gonadotrope produces _ and stimulates _
FSH or LH
Gonads
Thyrotrope produces _ and stimulates _
TSH
Thyroid Gland
Corticotrope produces _ and stimulates _
ACTH
Adrenal cortex
Lactotrope produces _ and stimulates _
Prolactin
Mammary Gland
Somatotrope produces _ and stimulates _
GH
Somatic Cells (to grow)
Hypothalamic pathway of dopamine
The hypothalamus secretes dopamine which…
Inhibits the release of prolactin from the anterior pituitary gland
Prolactin will stimulate the breast to produce milk
↑ Dopamine → ↓prolactin seceion and milk production
Hypothalamic pathway of TRH
The hypothalamus secretes TRH which…
stimulates the anterior pituitary gland to secrete TSH.
TSH stimulates the thyroid gland to release T3 and T4.
T3 and T4 impact many tissues
The thyoid axis
Hypothalamic pathway of CRH
The hypothalamus releases CRH which…
will stimulate the anterior pituitary gland to secrete ACTH
ACTH travels to the adrenal cortex where cortisol is released
Cortisol impacts many tissues
Adrenal Axis
Hypothalamic pathway of Somatostatin
The hypothalamus secretes Somatostatin which…
inhibits GH release from the anterior pituitary gland.
GH will stimulate the liver to secrete IGF-1.
↑ somatostatin → ↓GH and IGF-1
Hypothalamic pathway of GHRH
The hypothalamus secretes GHRH which…
stimulates GH release from the anterior pituitary gland.
GH will stimulate the liver to secrete IGF-1
GH and IGF-1 impact many tissues
Growth Axis
Hypothalamic pathway of GnRH
The hypothalamus secretes GnRH which…
will stimulate the anterior pituitary gland to secrete oth FSH and LH.
FSH and LH will stimulate the testes and ovaries to release androgens, estrogens, and progesterone.
Androgens, estrogens, and progesterone impact many tissues
Gonadal axis
What is the function of tropic cells?
Stimulate other cells
Basic Growth Hormone Axis
Hypothalamus → secretes GHRH → stimulates Anterior Pituitary → secretes GH → stimulates Liver/Bone → secretes IGF-1 → IGF-1 travels through the blood → stimulates SSTN → inhibits GH secretion from AP
Define
Anabolic
Builds up
Define
Catabolic
Break down
How can GH promote both anabolic and catabolic processes?
GH is anabolic in fed state (caloric excess)
GH is catabolic in fasted state
What are the effects of GH and IGF-1 when GH is in the fed state (anabolic) on the liver?
GH stimulates liver → ↑ RNA synthesis, Protein Synthesis, IGFBP, IGFs → stimulates release of IGF-1
What are the effects of GH and IGF-1 when GH is in the fed state (anabolic) on bone, heart, and lung?
GH and IGF-1 stimulate Bone, heart, lung → ↑Protein/DNA/RNA Synthesis, Cell size and number (↑Organ size and function)
What are the effects of GH and IGF-1 when GH is in the fed state (anabolic) on muscle?
GH and IGF-1 stimulate Muscle → ↑Amino Acid uptake, Protein Synthesis (↑Lean body mass)
What are the effects of GH and IGF-1 when GH is in the fed state (anabolic) on chondrocytes in bone?
GH and IGF-1 stimulate chondrocytes in bone → ↑Amino Acid uptake, ↑Protein/DNA/RNA Synthesis, ↑Collagen, ↑Chondroitin sulfate, ↑Cell size and number (↑Linear Growth)
What organs/glands/cells do GH and IGF-1 stimulate when GH is in the fed state (anabolic)?
Kidney
Pancreas
Intestine
Islet cells
Parathyroid
Skin
Connective Tissue
When GH is in the fasted state (catabolic), what effect does it have on adipose tissue?
GH stimulates adipose tissue → ↓Glucose uptake, ↑Lipolysis; ↓Adiposy
When GH is in the fasted state (catabolic), what effect does it have on the liver?
GH stimulates Liver → ↑Gluconeogenesis → stimulates IGF-1 release → ↑Organ size/function, ↑Linear growth, ↑Lean body mass
When GH is in the fasted state (catabolic), what effect does it have on the muscle?
GH stimulates Muscle → ↓Glucose uptake → ↑Lean body mass
What is the effect of loss of GH during normal aging? What does it result in?
loss of GH during normal aging → ↓ lean muscle mass, ↑ fat mass, ↓ bone density
Causes: frality, muscle atrophy, relative obesity, ↑frequency of fractures and disordered sleep (old age)
How does GH secretion change throughout life?
GH rises after birth; higher [] than adults → levels out in childhood → Peaks during puberty → ↓ between puberty and adult life → stabilizes during adult life → declines in old age
GH Pathologies, disruption of homeostasis
GH oversecretion before puberty =
What does it cause?
Tall stature
GH Pathologies, disruption of homeostasis
GH oversecretion after puberty =
What does it call?
Acromegaly
↑Bone width
GH Pathologies, disruption of homeostasis
GH undersecretion =
What does it cause?
Short stature
GH Pathologies, disruption of homeostasis
GH receptor deficiency =
What does it cause?
Short stature (Laron Dwarfism)
Feedback Loops
What would you expect the concentration of GHRH, GH, IGF-1, and Somatostatin in someone with acromegaly relative to a “normal” patient? What would you expect for blood glucose, amino acids, and free fatty acids?
Low GHRH
High GH
High IGF-1
High Somatostatin
High Blood Glucose
Low Amino Acids
High Free Fatty Acids
Feedback Loops
What would you expect the concentration of GHRH, GH, IGF-1, and Somatostatin in someone with growth hormone deficiency relative to a “normal” patient? What would you expect for blood glucose, amino acids, and free fatty acids?
High GHRH
Low GH
Low IGF-1
Low Somatostatin
Low Blood Glucose
High Amino Acids
Low Free Fatty Acids
Feedback Loops
What would you expect the concentration of GHRH, GH, IGF-1, and Somatostatin in someone with growth hormone receptor deficiency relative to a “normal” patient? What would you expect for blood glucose, amino acids, and free fatty acids?
High GHRH
High GH
Low IGF-1
Low Somatostatin
Low Blood Glucose
High Amino Acids
Low Free Fatty Acids
Why is GHRH low in a patient with acromegaly relative to a normal patient?
GH feeds back to inhibit GHRH secretion
Why are blood free fatty acids high in a patient with acromegaly relative to a normal patient?
GH promotes lipolysis in adipose tissue, therby increasing fatty acids in blood
Why is IGF-1 high in a patient with acromegaly relative to a normal patient?
GH stimulates excess IGF-1 secretion
Why is Somatostatin high in a patientn with acromegaly relative to a normal patient?
excess GH triggers this inhibitor
Why is Blood Glucose high in a patient with acromegaly relative to a normal patient?
GH prevents insulin induced uptake of glucose
Why are Blood amino acids low in a patient with acromegaly relative to a normal patient?
GH promotes amino acid uptake into muscle
Why is GHRH high in a patient with GH Receptor Deficiency relative to a normal patient?
GH receptors are defective so the hypothalamus is not able to sense the high levels of GH
Why is IGF-1 low in a patient with GH Receptor Deficiency relative to a normal patient?
GH receptors are defective,so GH is unable to stimulate iGF-1 release
Why is Somatostatin low in a patient with GH Receptor Deficiency relative to a normal patient?
lack of GH activity leads to low SS
Why is Blood Glucose low in a patient with GH Receptor Deficiency relative to a normal patient?
GH is unable to prevent uptake into skeletal muscle and adipose, so glucose gets into muscle/adipose and leaves blood
Why are Blood amino acids high in a patient with GH Receptor Deficiency relative to a normal patient?
GH receptor defect prevents the muscle from taking up amino acids in the blood, leading to muscle mass
Why are Blood Free Fatty Acids low in a patient with GH Receptor Deficiency relative to a normal patient?
GH receptor defect reduces lipolysis in the adipose tissue, thus adipose tissue remains full of fat substrates
