Endocrine Lecture 2: Pituitary Gland

Question 1

The Hypothalamus and pituitary gland exert control over:

Answer 1

Thyroid
Adrenals
Gonads

Question 2

The Hypothalamic pituitary axis (HPA):

Answer 2

Responsible for brain-endocrine interactions

Question 3

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.

Answer 3

Hypothalamus

Pituitary

Question 4

The Pituitary gland is located:

Answer 4

Rests in the sphenoid bone in an area called the Sella Tursica.

Question 5

What are the 4 divisions of the pituitary gland?

Answer 5

1. Anterior pituitary (AKA Adenohypophysis): Largest
2. Pars Intermedius: gone after fetal development
3. Pars Tubularis: Highly vascular, no known hormones secreted.
4. Posterior pituitary: Neurohypophysis

Question 6

the anterior pituitary is connected to the hypothalamus via:

Answer 6

A portal venous network

Question 7

The anterior pituitary is responsible for regulation of the:

Answer 7

• Thyroid
• Adrenal
• Mammary glands

Also: release of growth hormone, gonads, and melanocytes.

Question 8

What are the 5 cell types of the Anterior pituitary?

Answer 8

1. Somatotropes: Most abundant, secrete growth hormone
2. Corticotropes: secrete Adrenocorticotropic Hormone (ACTH)
3. Thyrotropes: Secrete Thyroid Stimulating Hormone (TSH)
4. Gonadotropes: Secretes Luteinizing and Folicle Stimulating Hormone (LH & FSH)
5. Lactotropes: Secrete Prolactin (PRL)

Question 9

Posterior Pituitary (AKA Neurohyphysis) produces what 2 hormones?

Answer 9

1. Oxytocin

2. Vasopressin (Anti-Diuretic Hormone)

Question 10

Oxytocin and Vasopressin (ADH) are produced in the _____ and secreted by ______?

Answer 10

Hypothalamus and secreted by the Posterior Pituitary. they are transported intracellularly from the Hypothalamus to the pituitary for secretion

Question 11

The dominant site of Vasopressin (ADH) synthesis is?

Answer 11

the Supraoptic Nucleus in the Hypothalamus.

Question 12

Functions of Vasopressin (ADH):

Answer 12

-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

Question 13

Stimulus for release of Vasopressin (ADH):

Answer 13

• 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.

Question 14

Syndrome of Inappropriate ADH (SIADH):

Answer 14

• 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

Question 15

Na > _____ mEq/L is safe for elective procedures

Answer 15

130

Question 16

Na <130 may lead to:

Answer 16

cerebral edema.

Hyponatremia must be corrected SLOWLY!!

Question 17

Symptoms of hyponatremia do not generally show up until Na is at or below _____mEq/L.

Answer 17

125

Question 18

Signs/symptoms of hyponatremia:

Answer 18

Mild: Anorexia, nausea, weakness
Moderate: Lethargy, confusion
Severe: seizures, coma, death

Question 19

Central Pontine Myelinolysis:

Answer 19

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.

Question 20

Diabetes Insipidus (DI)

Answer 20

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.

Question 21

Transient diabetes Insipidus is common with what?

Answer 21

Head injuries.

Question 22

Causes of nephrogenic diabetes insipidus:

Answer 22

• chronic renal disease
• lithium toxicity
• hypercalcemia, hypokalemia
• Tubulointerstitial disease

Question 23

how is anesthesia influenced by HyperNatremia?

Answer 23

• Increased MAC with decreased uptake of inhalation agents due to low cardiac output.
• Associated hypovolemia will decease doses for iv agents

Question 24

Surgery should be postponed for a Na of greater than_____?

Answer 24

greater than 150 mEq/L

Question 25

Risk factors for developing Central Pontine Myelinolysis:

Answer 25

• 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.