Neuro-endocrinology Flashcards
What are some neuroendocrine structures?
- Neuroendocrine cells of the hypothalamus
- Pineal gland
- Adrenal medulla
NOTE: Oxytocin and vasopressin are neurohormones from the posterior pituatary.
Hypothalamic releasing hormones are synthesized in the hypothalamus an secreted from axonal endings at the ______.
Median eminence
What is the course of hypothalamic releasing hormones?
- Hypothalamus
- Secreted by axon endings at the median eminence
- Enter primary plexus of fenestrated capillaries
- Conveyed from the median eminence to a seconday capillary plexus by the hypophyseal protal vessels
- Diffuse out of the vasculature and bind to their specific receptors on specific cell types within the anterior pituatary
What is the structure found between the hypothalamus and the anterior pituatary called?
Pituatary stalk
NOTE: The pituatary stock is somewhat fragile and can be disrupted by physical trauma, surgery, or hypothalamic disease
Oxytocin and vasopressin are made by the ________.
Hypothalamus
REMEMBER: Oxytocin and vasopressin are only stored by the posterior pituatary. The posterior pituatary makes nothing.
If the pituatary stalk is damaged what is one of the first things you will see?
Hyperprolatinemia
Polyuria and polydypsia (as a result of blocked ADH release)
Functions of the median eminence
What two hormones stimulate the release of prolactin?
PRFs and TRH
____________ is the most important regulator of prolactin.
Dopamine
_______________ inhibits GH.
Somatostatin
What is the ACTH receptor found at the target?
MC2R (Gs-linked GPCR)
NOTE: The target endocrine gland are the zona fasciculata and zona reticularis of the adrenal cortex
What is the target of TSH?
Thyroid epithelium
What is the receptor for TSH?
TSH receptor (Gs-linked GPCR)
What are the receptors for FSH and LH?
FSH and LH receptors (Gs-linked GPCRs)
What is the GH receptor?
GH receptor (JAK/STAT-LINKED cytokine receptor)
What is the prolatin receptor?
PRL receptor (JAK/STAT-linked cytokine receptor)
What are the most common anterior pituaitary disorders?
Hyperprolactinemia
Growth Hormone Disorders
Pituatary Adenomas
Hypopituatarism
What major factors stimulate prolatin secretion?
Pregnancy and nursing
Physiologic stress
Estrogen use
Hypothyroidism
How does somatostatin inhibit GH?
By inhibiting PKA
Stimulators of GH
Stress
Exercise
Starvation
Acute hypoglycemia
Aging
Increased amino acids
Decreased fatty acids
Sleep
Ghrelin
NOTE: If you suspect that a child has short stature, you can put the child on an exercise device and growth hormone levels should increase. If the levels don’t increase with exercise you know something is wrong and you can supplement growth hormone.
Inhibitors of GH
Hyperglycemia
Increased fatty acids
IGF
Glucocorticoids
____________ is the transporter for glucose in the muscle and adipose tissue.
GLUT-4 (insulin-_dependent)_
NOTE: Growth hormone inhibits glucose uptake inake in muscle and adipose tissue
____________ is the glucose tranporter for glucose in the liver.
GLUT 2 insulin independent)
What affect does GH have on adipose tissue, liver and muscle?
Adipose tissue
- Decrease glucose uptake
- Increase lipolysis
Liver
- Increase in RNA synthesis
- Increase in protein synthesis
- Increase in gluconeogenesis
- Increase in IGFBP
- increase in IGFs
Muscle
- Decrease in glucose uptake
- Increase in amino acid uptake
- Increase in protein synthesis
Muscle
IGFs and GH work together to increase the organ size and function of which organs?
Kidney
Pancreas
Intestine
Islets
Parathyroids
Skin
Connective tissue
Bone
Heart
Lung
GH causes lenthening of bone at the __________.
Epipheyseal plates
Side effects of too much GH
Ketogenesis
Hyperglycemia
Heat issue (like cardiomyopathy
What affect does nutrition have on hormone secretion?
Eating a balanced meal
- Proteins stimulate GH, insulin, and glucagon secretion
- GH inturn produces IGF
Eating a high calorie, high carbohydrate, low protein meal
- Stimulates insulin
- Inhibit GH and IGF
During fasting
- Increases GH
- Decreases insulin
GH cannot stimulate IGF production in the absence of _________.
Insulin
Causes of gigantism
- Pituatary GH excess
- Hypothalamic GHRH excess
- Ectopic source of GH or GHRH
NOTE: Gigantism is only seen in growing children
What tests are used for determining GH hypersecretion
- Serum IGF
- Oral glucose tolerance test
- Pituatary MRI
What tests can be used to test for GH deficiency?
Exercise
Insulin-induced hypoglycemia
Amino acids
Which hormones are important for growth?
IGFs
GH
T3
Sex steroids
Insulin
What are some endocrine causes of growth failure?
Hypothyroidism
Cushing syndrome
Growth hormone deficiency
Precocious puberty
Common causes of hypopituitarism
- Pituatary adenoma and other types of pituatary masses
- Pituitary infarction (Sheehan’ssyndrome) or hemorrhage
- Mutations is genes that encode transcription factors such as PROP-1
What affects for hyperprolactinemia have on FSH and LH in females?
Causes a decrease in both
SIADH
Excessive vasopressin release that is defined as less-than-maximally-dilute urine in the presence of plasma hypoosmolality without volume depletion or overload
NOTE: SIADH is one of the many causes of hyponatremia
Why is SIADH associated with euvolemia?
There should be an increase in volume but when volume is high ANP causes a release in Na+
NOTE: Aldosterone is also supressed, which explains why the K+ levels are normal
Treatment of SIADH
- Restrict fluid intake
- Increase solute intake with urea or a combination of low-dose loop diuretics and oral sodium chloride
- Treat underlying cause
After a desmopressin test, urine osmolality is >300. What type of diabetes is present?
Central diabetes insipidus
After a desmopressin test, urine osmolality is <300. What type of diabetes is present?
Nephrogenic diabetes insipidus
After a desmopressin test, urine osmolality is >800. What condition is present?
Primary polydipsia
