Hypothalamic Pituitary Relationships & Biofeedback Pt.1 Dr. Creamer Flashcards
What is the physical connection between the hypothalamus and the pituitary gland>
Hypophyseal stalk
Why do tumors in pituitary gland affect sight?
Close relationship to the optic nerves tumors can expand and compress them
How do hormones get from the hypothalamus to the posterior pituitary gland?
- Travel down the axons from the hypothalamus into the posterior pituitary to be stored
- Supraoptic nuclei releases ADH
- PVN releases oxytocin
How do hormones get from hypothalamsu to the anterior pituitary?
Hypothalamic neurons produce releasing or releasing inhibiting hormones and release them into the portal
- Pituitary is connected to hypothalamus by hypothalamic hypophysial portal system
What is the ACTH family?
Corticotrophs which produce ACTH
TSH FSH LH family?
- Thyrotrophs secrete TSH
- Gonadotrophs secrete FSH and LH
- Alpha subunit of these are shared but differ in beta subunit
What is the GH prolactin family?
- Peptide hormones
- Somatotrophs produce GH
- Lactotrophs produce prolactin
What hormones are secreted by the anterior pituitary?
- FSH
- LH
- GH
- ACTH
- TSH
- Prolactin
What hormones are secreted by the hypothalamus, what cell do they target and what is effect?
- TRH targets thyrotrophs in AP to release TSH
- CRF targets corticotrophs to release ACTH
- GnRH targets gonadotrophs to release LH FSH
- GHRH targets somatotrophs to release GH
- GHIH(Somatostatin) targets somatotrophs to decrease GH
- PIF (Dopamine) targets lactotrophs to decrease PRL
- TRH targets lactotrophs when elevated to release PRL
What hormone inhibits growth hormone secretion and prolactin?
- Somatostatin for GH
- Dopamine for prolactin
Describe primary secondary and tertiary endocrine disorders.
- Primary: defects in the peripheral gland
- Secondary: defects in the pituitary releasing hormones
- Tertiary: defects in the hypothalamus stimulating release of stimulating hormone
Describe the axis for GnRH in testes.
- GnRH released in a pulsatory fashion from the hypothalamus to the ant. pit.
- LH FSH are released (Tropic hm released to periphery)
- LH goes to Leydig cell to stimulate testosterone release which works on Sertoli cells
- FSH targets Sertoli cells to make angrogen binding protein and influences spermatogenesis
- Sertoli cell produces inhibin which negatively feeds back to the pituitary to decrease FSH secretion
- Testosterone negatively feeds back to decrease LH and GnRH
Describe HPG axis in ovaries.
- GnRH released pulsatile from hypotlalamus to pituitary
- Pit releases LH and FSH
- FSH to granulosa cells and cause synthesis of estrogens which allows for follicle dev
- Granulosa cell produces inhibin which acts son pituitary to decrease FSH
- Also produces Progestins and estrogens which inhibit FSH and LH as well as the hypothalamus release of GnRH
- LH to Theca cells which produces androgens
- Androgens go to Granulosa cell for conversion to estrogens
- Midcycle estrogen production is upregulated and becomes positive feedback on hypothalamus and pituitary allwong for oocyte to mature and produce LH surge (ovulation)
- FSH to granulosa cells and cause synthesis of estrogens which allows for follicle dev
What is Acromegaly?
- excess growth of soft tissues and cartilage in hands and feet
- due to excessive GH which can decrease tissues sensitivity to insulin producing hyperinsulemia
What are the direct targets of GH and how is it regulated?
- Liver and bone are direct targets and respond via Jak-STAT pathway which causes release of IGF-1
- IGF-1 negative fb on hypo and pit to decrease GH release2
How does GH secretion change daily?
Secretion flucuates thorughout the day
- peaks during sleep and exercise
What acute physiological conditions can stimulates GH release?
- Fasting/hunger/starving
- Hypoglycemia
- Hm of pberty
- exercise
- sleep
- stress
If there is excess of GH prior to closure of epiphyses what occurs?
- Gigantism
If GH is secreted in excess after epiphyseal plate closure what results?
Acromegaly
If there is excess systemic GH what could be happening?
Growth hm insensitivity at the liver, a primary endocrine disorder
- Liver is unresponsive to GH so IGF-1 isn’t produced which is one of the negative FB mechanisms to decrease GH secretion
What would a secondary endocrine deficiency of GH look like?
- Low levels of GH and IGF-1
- Pituitary isn’t releasing GH so IGF-1 isn’t being produced
What does a tertiary deficiency of GHRH look like?
- No GHRH so no GH therefore no IGF-1
If you are in a fed state (high blood sugar, high amino acids) what will the liver do in response to GH?
Respond to GH by producing IGF-1 to do Lypolysis Mitogenesis and differentiation
If you are in unfavorable growth conditions such as adaquate insulin and blood sugar levels, but low protein intake, what will the liver do in response to GH?
- GH is sinhibited and liver does not produce IGF-1
- Lipogenesis and carb storage occurs
What happens if you have low carbs and high protein intake in regards to liver and GH?
- Metabolism shifts to use lipids as energy source
- GH levels increase and IGF-1 is produced
- Lipolysis, Ketogenic metabolism, and diabetogenic occurs
- this can promote insulin insensitivity
How is prolactin inhibitetd?
Dopamine and it is the main stimulation for it unless breast feeding
Why can breast feeding women have lactational amonerrhea?
- Prolactin negatively feeds back on hypothalamus to cause a decrease in GnRH which will decrease FSH and LH from ant. pit
- alters follicular cyle
How is prolactin produced and where?
- Produced in cell body of neurons in the hypothalamus as Prepro-oxyphysin
- Pre-pro protein is cleaved and packed in vesicles and travel down axon
- modification into pro hormone occurs in vesicles and then to mature oxytocin
- Reaches posterior pituitary stored in vesicles until released to act on breast and uterine tissues
Actions of Oxytocin?
- Milk ejection
- milk letdown stimulates myoepithelial cell contraction
- stimulated by suckling sight sound or smell of infant
- Uterine contractions
- stimulates by dilation of cervix or orgasm
- stimulating contractions creating a positive FB loop
