Hypothalamic-Pituitary Relationships and Biofeedback Part 1 (Creamer) Flashcards
What is the physical connection between the hypothalamus and the pituitary gland?
Hypophysial stalk
If there are tumors in the pituitary area, what symptoms can it cause?
Due to its proximity, the pituitary gland can put pressure to the optic nerves and can cause visual problems and dizziness.
What are the nucleus in the hypothalamus that send axons to the posterior pituitary
Supraoptic nucleus (SON)
Paraventricular nucleus (PVN)
What do the paraventricular nucleus and supraoptic nucleus produce and secrete to the hypothalamus?
Oxytocin & ADH (Vasopressin)
What does the anterior pituitary secrete (6 tropic hormones)?
ACTH
TSH
FSH
LH
GH
Prolactin
How is the anterior pituitary connected to the hypothalamus
Hypothalamic-hypohysial portal blood vessels
The connections between the hypothalamus and posterior lobe are ____?
neural
The connections between the hypothalamus and anterior lobe are ____?
neural and hormonal
What hormone is a negative inhibitor of growth hormone?
Somatostatin (GHIH)
IGF-1
What is a primary endocrine disorder?
Defect in peripheral endocrine gland that can cause low or high levels of hormones
What is a secondary endocrine disorder?
Defect in pituitary gland that can cause low or high levels of hormones
What is a tertiary endocrine disorder?
Defect in hypothalamus that can cause low or high levels of hormones
In the HPG axis, what is the major hypothalamic hormone
GnRH
In the HPG axis, what is major pituitary hormone?
FSH and LH
In the HPG axis, what is the peripheral target organ for males?
Testes
LH targets Leydig cells
FSH targets Sertoli cells
How is the HPG axis in males controlled?
Testosterone from Leydig cells inhibits GnRH and LH
Inhibin from the Sertoli cells inhibits FSH
In the HPG axis, what is the peripheral target organ for females?
Ovaries
LH targets Theca cells
FSH targets Granulosa cells
How is the HPG axis in females controlled?
Progestins and estrogen from granulosa cells inhibit GnRH, LH & FSH.
Also, inhibin from granulosa cells inhibits FSH & LH during ovulation.
What happens if GnRH release is inhibited?
Reduce production of gametes and affect fertility
What causes acromegaly?
Prolonged and excessive secretion of growth hormone in adult life
What are symptoms of acromegaly?
Large hands, feet, and head
Prominent lower jaw
Cardiomegaly
Organomegaly
Hypertension
What regulates the release of growth hormone
Growth hormone release hormone (GHRH) & Growth hormone inhibiting hormone (GHIH) = somatostain. Both released from hypothalmus
What is another name for GH
Somatotropin
Explain the direct and indirect targets of GH
Direct: Targets bone and muscle
Indirect: Targets liver which then secrets IGF-1 which can target almost every cell type in body (PRIMARY METHOD)
What can stimulate release of growth hormone?
Fasting/hunger/starvation
Hypoglycemia
Puberty
Exercise
Sleep
Stress
What does growth hormone induce?
Growth
Cell Reproduction
Metabolism
How does the liver induce a negative feedback on the hypothalamus and pituitary gland?
Insulin-like growth factor 1 (IGF-1) inhibits GHRH (hypothalamus) & GH (AP) but stimulates GHIH
If there is an excess of growth hormone noticed before the closure of the bone epiphyses due to IGF-1, what do you expect to see?
Gigantism
If there is an excess of growth hormone noticed after the closure of the bone epiphyses, what do you expect to see?
Acromegaly
What happens when an individual has adequate carbohydrate and protein intake?
IGF-1 is produced leading to mitogenesis, lipolysis, and differentiation
What happens when an individual has adequate carbohydrate intake but not enough protein intake?
GH production is inhibited due to inadequate amino acid availability so liver will not produce IGF-1 leading to lipogenesis and carbohydrate storage (weight gain)
What happens when an individual has adequate protein intake but not enough carbohydrate intake?
Increased GH levels so liver will produce IGF-1 leading to lipolysis, ketogenic metabolism and diabetogenic effects
Shift in metabolism, by usig lipids as an energy source
How does GH promote insulin insensitivity
A shift in using lipids as an energy source leads to a decrease in glucose uptake by cells.
What are the metabolic functions of growth hormone?
- Diabetogenic effect: increase of blood glucose and insulin levels
- Increase in protein synthesis and organ growth
- Increase in linear growth: stimulates DNA, RNA, and protein synthesis
During which parts of the day does GH secretion peak?
Exercise
Beginning of sleep
Why do we give an oral glucose tolerance test to someone suspected to have acromegaly?
Glucose typically shuts down secretion of GH. We can give glucose to patients suspected of acromegaly to see if blood GH levels will decrease. If they don’t decrease, patient might have acromegaly.
Why do we look at IGF-I levels when suspecting a diagnosis of acromegaly?
IGF-1 levels remain constant during the day while GH levels fluctuate.
How does the regulation of prolactin secretion differ from the other AP hormones
Prolactin is regulated through negative inhibition by dopamine.
Dopamine suppresses it’s release
What is the negative feedback activity of prolactin
Inhibits GnRH (LH and FSH) release which decrease reproductive function and suppresses sexual drive (This is a good thing right after a pregnancy)
What is the main inhibitor of prolactin secretion?
Dopamine
Describe the production and release of oxytocin from the posterior pituitary
- Produced in the hypothalamus as prepro-oxyphysin
- Cleaved and transported to posterior pituitary in vesicles where it is stored in it’s active form
- Released as oxytocin
What are the actions of oxytocin?
Milk ejection
Uterine contractions (postitive feedback)
