Lecture 10: Hypothalamic-Pituitary Relationships and Biofeedback Part 1 Flashcards
What is the physical connection between the hypothalamus and the pituitary gland?
Hypophyseal 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 does the supraoptic nucleus produce and secrete?
ADH into posterior pituitary
What does the paraventricular nucleus produce and secrete?
Oxytocin into posterior pituitary
What does the anterior pituitary secrete (6 tropic hormones)?
ACTH TSH FSH LH GH Prolactin
The connections between the hypothalamus and posterior lobe are ____?
neural
The connections between the hypothalamus and anterior lobe are ____?
neural and endocrine
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 from 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 and LH
Inhibin also from granulosa cells inhibits LH
*during ovulation, there can be a positive feedback loop with estrogen
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 does growth hormone target?
Liver
Bone
What can stimulate release of growth hormone?
Fasting/hunger/starvation Hypoglycemia Puberty Exercise Sleep Stress
What does growth hormone induce?
Growth
Cell Reproduction
Metabolism
What is hypertrophy?
Increase in the size or volume of cells
What is hyperplasia?
Increase in number of cells
What can treat defective release of GHRH?
Semorelin
What can treat defective release of GH?
Somatropin
Somatrem
What can treat the failure of the release of IGF-1?
Mecasermin
If there is an excess of growth hormone noticed before the closure of the bone epiphyses, 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?
IGF-1 is not produced leading to lipogenesis and carbohydrate storage (weight gain)
What happens when an individual has adequate protein intake but not enough carbohydrate intake?
IGF-1 is produced leading to lipolysis, ketogenic and diabetogenic metabolism
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.
What three components are requires to diagnose acromegaly?
Increased levels of IGF-1
Failure to suppress serum GH
Pituitary enlargement on MRI
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.
What does prolactin suppress?
GnRH (LH and FSH)
decrease reproductive function and suppresses sexual drive (This is a good thing right after a pregnancy)
What stimulates prolactin secretion?
Pregnancy (estrogen) Breast feeding (suckling) Sleep Stress TRH
What is the main inhibitor of prolactin secretion?
Dopamin
Somatostatin
What are some examples of hyperpituitarism?
Cushing’s Disease: Increased ACTH
Prolactinoma: Increased prolactin
Acromegaly/Gigantism: Increased GH
What are some main causes of hypopituitarism?
Brain damage
Pituitary tumors
What are the actions of oxytocin?
Breasts: Milk letdown
Uterine contractions
