Endocrine Lecture 2: Pituitary Gland Flashcards
The Hypothalamus and pituitary gland exert control over:
Thyroid
Adrenals
Gonads
The Hypothalamic pituitary axis (HPA):
Responsible for brain-endocrine interactions
The ______ is the coordinating center of the endocrine system, it consoidates signals from upper cortical inputs, autonomic functions, environmental cues, and peripheral endocrine feedback. The ______ releases hormones that influence other endocrine systems based on influence from the above mentioned structure.
Hypothalamus
Pituitary
The Pituitary gland is located:
Rests in the sphenoid bone in an area called the Sella Tursica.
What are the 4 divisions of the pituitary gland?
- Anterior pituitary (AKA Adenohypophysis): Largest
- Pars Intermedius: gone after fetal development
- Pars Tubularis: Highly vascular, no known hormones secreted.
- Posterior pituitary: Neurohypophysis
the anterior pituitary is connected to the hypothalamus via:
A portal venous network
The anterior pituitary is responsible for regulation of the:
- Thyroid
- Adrenal
- Mammary glands
Also: release of growth hormone, gonads, and melanocytes.
What are the 5 cell types of the Anterior pituitary?
- Somatotropes: Most abundant, secrete growth hormone
- Corticotropes: secrete Adrenocorticotropic Hormone (ACTH)
- Thyrotropes: Secrete Thyroid Stimulating Hormone (TSH)
- Gonadotropes: Secretes Luteinizing and Folicle Stimulating Hormone (LH & FSH)
- Lactotropes: Secrete Prolactin (PRL)
Posterior Pituitary (AKA Neurohyphysis) produces what 2 hormones?
- Oxytocin
2. Vasopressin (Anti-Diuretic Hormone)
Oxytocin and Vasopressin (ADH) are produced in the _____ and secreted by ______?
Hypothalamus and secreted by the Posterior Pituitary. they are transported intracellularly from the Hypothalamus to the pituitary for secretion
The dominant site of Vasopressin (ADH) synthesis is?
the Supraoptic Nucleus in the Hypothalamus.
Functions of Vasopressin (ADH):
-Increases permeability of the collecting ducts, increases free water reabsorption
- increases urine osmolality
- decreases plasma osmolality
- increases ECF volume
most potent vasoconstrictor in the body.
V1 receptor: pressor effect
V2 receptor: ADH effect
Stimulus for release of Vasopressin (ADH):
- Osmoreceptor in the Hypothalamus are activated by plasma osmolality >290 mOsm/kg. Normal=285
- Decreased ECF volume activates stretch receptors in the great veins, atria, pulmonary vessels or ADH release.
- Other stimulators: Angiotensin II, nicotine, nausea, pain, stress.
Release is depressed by decreased plasma osmolality, increased ECF volume and EtOH.
Syndrome of Inappropriate ADH (SIADH):
- Increased release of ADH
- Water retention, hypoosmolar (dilute) plasma.
- Hyponatremia with decreased urine production, concentrated urine.
Caused by pituitary tumors.
Sequela: CNS disorders, cold stress: trauma, drug induced, squamous cell lung CA
Na > _____ mEq/L is safe for elective procedures
130
Na <130 may lead to:
cerebral edema.
Hyponatremia must be corrected SLOWLY!!
Symptoms of hyponatremia do not generally show up until Na is at or below _____mEq/L.
125
Signs/symptoms of hyponatremia:
Mild: Anorexia, nausea, weakness
Moderate: Lethargy, confusion
Severe: seizures, coma, death
Central Pontine Myelinolysis:
Rapid correction of hyponatremia is associated with demylinating lesion in the pons.
-seen if increased greater than 0.5 mEq/L/Hr
-TURP syndrome: absorption of low sodium solution dilutes blood.
Diabetes Insipidus (DI)
ADH (Vasopressin) deficiency. Either through central (inability to release ADH-most common) or inability of kidney to respond (renal).
-increased thirst, dilute urine, excretion of large amounts of of hypoosmotic urine. Hyperosmotic plasma.
Desmopressin (DDVAP) treats central DI and demeclocycline for renal.
Transient diabetes Insipidus is common with what?
Head injuries.
Causes of nephrogenic diabetes insipidus:
- chronic renal disease
- lithium toxicity
- hypercalcemia, hypokalemia
- Tubulointerstitial disease
how is anesthesia influenced by HyperNatremia?
- Increased MAC with decreased uptake of inhalation agents due to low cardiac output.
- Associated hypovolemia will decease doses for iv agents
Surgery should be postponed for a Na of greater than_____?
greater than 150 mEq/L
Risk factors for developing Central Pontine Myelinolysis:
- serum sodium less than 120 for more than 48hrs
- Aggressive IV fluid therapy with hypertonic saline solutions
- Development of hypernatremia during treatment.
symptoms usually occur 48-72 hours post therapy.