PITUITARY DISORDERS Flashcards
What is the other name for the pituitary gland?
Hypophysis
What is the name of the system of blood vessels connecting the hypothalamus and the pituitary gland?
Hypophyseal portal system
What is the other term for the anterior pituitary?
Adenohypophysis
Name the 7 hormones produced by the anterior pituitary
- GH (growth hormone)
- TSH (thyroid stimulating hormone)
- LH (luteinizing hormone)
- FSH (follicle stimulating hormone)
- PRL (prolactin)
- ACTH (adrenocorticotropic hormone)
- MSH (melanocyte stimulating hormone)
What is the other name for the posterior pituitary?
Neurohypophysis
Name the 2 hormones secreted by the posterior pituitary
- Oxytocin
- ADH (antidiuretic hormone)
Why is the pituitary especially sensitive to changes in perfusion during pregnancy?
During pregnancy the pituitary gland increases in size without an increase in blood supply
What is the name of hypopituitarism secondary to an obstetric hemorrhage?
Sheehan syndrome
Why does Sheehan syndrome result in failure to lactate?
Decreased prolactin secretion
Why does Sheehan syndrome result in amenorrhea, infertility, and breast/vaginal atrophy?
Decreased LH and FSH secretion
Why does Sheehan syndrome result in hypothyroidism?
Decreased TSH secretion
Why does Sheehan syndrome result in low blood pressure and low blood sugar?
Decreased ACTH (adrenocorticotropic hormone) secretion > adrenal insufficiency > decreased glucocorticoids
What is the name of inability to concentrate urine secondary to insufficient ADH (antidiuretic hormone)?
Diabetes insipidus
What are 3 kinds of diabetes insipidus?
- Central DI
- Nephrogenic DI
- Psychogenic DI
Which type of DI is caused by a brain lesion interfering with ADH synthesis?
Central DI (vasopressin deficiency)
Which type of DI is caused by kidney disease/toxicity?
Nephrogenic DI (vasopressin resistance)
Which type of DI is caused by compulsive thirst, resulting in a decreased concentration of ADH due to dilution?
Psychogenic DI (primary polydipsia)
Besides polyuria and polydipsia, what are 4 symptoms of DI?
- Dehydration
- Hypernatremia
- Hydronephrosis
- Bladder distension
How does tracking intake/output help to determine the etiology for DI?
In central and nephrogenic DI, the urine output will remain the same even with a decrease of intake
How would a trial of ADH/Pitressin help determine the etiology for DI?
In central DI the problem is not enough ADH so hormone replacement would be beneficial.
In nephrogenic DI the problem is the kidneys are resistant to ADH so hormone replacement would have no effect.
How would MRI help to determine the etiology for DI?
A healthy posterior pituitary appears very bright on MRI. In central DI it does not appear this way.
What is the term for a test using various stimulating agents to trigger release of GH from the anterior pituitary?
Pituitary stimulation test
In Sheehan syndrome, how would the pituitary appear on MRI?
“Empty sella”: appears shrunken/flattened
What kind of solution is used to correct dehydration in diabetes insipidus?
Hypotonic solution (causes pull of fluid out of vasculature and into cells)
What is the main target organ of growth hormone?
Liver
What are 2 functions of growth hormone?
- Stimulates liver to produce insulin-like growth factor (IGF-1)
- Increases lipolysis and glycogenolysis to make ATP
What is the purpose of insulin-like growth factor (IGF-1)?
Anabolic functions such as cell growth/reproduction, protein synthesis
What are 2 hypothalamic hormones that regulate the release of growth hormone?
- GHRH (growth hormone releasing hormone)
- Growth hormone inhibiting hormone (somatostatin)
What is the cause for excessive production of growth hormone in hyperpituitarism?
Benign somatotropic tumour of the anterior pituitary
What are 2 reasons growth hormone is considered diabetogenic?
- It promotes glycogenolysis causing hyperglycemia
- Hyperglycemia causes excess insulin release
In diagnosis of hyperpituitarism, why are IGF-1 and GH levels tested after administration of oral glucose?
Growth hormone secretion should normally be suppressed by increased blood glucose through negative feedback
What are 2 classes of drugs used to treat hyperpituitarism?
- Growth hormone inhibiting hormone analogs
- Growth hormone receptor antagonists
What is the term for hypersecretion of growth hormone during childhood and adolescence?
Pituitary gigantism
What are 2 diseases that individuals with pituitary gigantism have an increased risk for?
- Cardiomegaly
- Heart failure
