Chapter 17: Hormones - Hypothalamus and Pituitary

Question 1

Adenohypophysis

Answer 1

anterior pituitary gland

Question 2

Neurohypophysis

Answer 2

posterior pituitary gland

Question 3

Growth Hormone from Pituitary

Answer 3

Somatotrophs (cells) of adenohypophysis synthesize and release Growth Hormone (GH)

Release is stimulated by hormone from hypothalamus (peptide), Growth Hormone Releasing Hormone (GHRH) from the hypothalamus

Growth hormone works through:
Also known as somatotropin (STH),
Second messenger mechanism,

Question 4

Regulation and Effects of Growth Hormone

Answer 4

Stimulus for Release (what causes its release into blood):
Deep sleep
↓ decreased [glucose] in blood (called hypoglycemia)
↑ increased secretion of Growth Hormone Releasing Hormone (from hypothalamus)
↓ decreased Growth Hormone Inhibiting Hormone
↓ deceased IGFs (Insulin Growth Factors)

Effects immediate and long-term:
↑ increased [glucose] in blood (can cause hyperglycemia)
↑ increased fat catabolism (breakdown of fats from adipose tissue)
Stimulates tissue growth longitudinal (before puberty) and horizontal (after puberty – increased bone density)
Antagonistic to insulin in reference to blood glucose concentration

Question 5

Acromegaly

Answer 5

Age-progression of a woman with hypersecretion of GH characterized by large and coarse jaw and abnormal enlargement of bones. Enlargement of vertebrae may result in hump.

Question 6

Tetraiodothyronine (T4), or thyroxine:

Answer 6

4 iodine atoms,
~20 times more abundant than T3,
It is the precursor for T3

T3 and T4 are attached to globulin molecules and transported in blood plasma.

Question 7

Triiodothyronine (T3):

Answer 7

3 iodine atoms,
Principal thyroid hormone,
Binds efficiently to nuclear receptors in target cells.

Question 8

Endemic Goiter

Answer 8

Due to low iodine in diet is common in underdeveloped countries

Iodine supplements will restore normal T3/T4 levels in most cases

Question 9

Negative Feedback of Thyroid Gland

Answer 9

Its stimulated by Thyroid Stimulating Hormone (TSH) from adenohypophysis,

TSH is synthesized by thyrotrophs (cells) found in adenohypophysis,

TSH is stimulated by another hormone – Thyroid Releasing Hormone TRH (from hypothalamus).

Question 10

Regulation and Effects of Thyroid Hormone

Answer 10

Stimulus for Release (what causes its release into blood):
↓ decreased [glucose] in blood (called hypoglycemia)
↑ increased secretion of Thyroid Stimulating Hormone (from adenohypophisis)
↑ increased secretion of Thyroid Releasing Hormone (from hypothalamus)

Effects immediate and long-term:
↑ increased [glucose] in blood (can cause hyperglycemia)
Acts on pituitary to secrete Growth hormone
↑ Increases catabolism and fat breakdown
↑ Increases activity, and temperature
Regulated by negative feed-back loop
Antagonistic to insulin in reference to blood glucose

Question 11

What do the levels of TRH, TSH and TH tell you as to where a tumor may be found?

Answer 11

Tumor on Adenohypophysis = Decreased TRH, Increased TSH and T3/T4

Question 12

Adrenocorticotropic Hormone (ACTH) from pituitary

Answer 12

Stimulates adrenal cortex

Corticotrophs (cells) of adenohypophysis synthesize and release a large protein that is ‘cut’ into Adrenocorticotropic hormone (ACTH) and Melanocyte-Stimulating Hormone (MSH)

Release is stimulated by hormone from hypothalamus (peptide), Corticotropic Releasing Hormone (CRH) from the hypothalamus,

Growth hormone works through:
Also known as somatotropin (STH),
Second messenger mechanism,

Question 13

Release of hormones from adrenal cortex:

Answer 13

Glucocorticoids from zona fasciculata primarily Cortisol (a hyperglycemic hormone)

Mineralcorticoids from zona reticularis primarily Aldosterone (conserves Na+ and water in body)

Androgens: Sex hormones such as testosterone and estrogen (in small quantities) from zona glomerulusa

Question 14

Mineralcorticoids – Aldosterone from Adrenal Cortex

Answer 14

Stimulus for Release (what causes its release into blood):
Increased ACTH secretion,
Increased K+ in blood
Decreased pH

Effects:
Increases Na+ reabsorption by the kidneys (sodium conservation),
Because Na+ is retained it Increases water retention
Promotes loss of K+ and H+ by he body (excreted in urine) to regulate pH and K+

Question 15

Glucocorticoids – Cortisol from adrenal Cortex

Answer 15

Stimulus for Release (what causes its release into blood):
Decreased glucose concentration in blood,
Increased ACTH secretion

Effects:
Increases glucose in blood (hyperglycemic hormone),
Decreases immune response,
Acts with epinephrine in the recovery from injury produced by inflammatory agents,
Secretion increases response to stress (and stress increases secretion – positive feedback loop).

Question 16

Gonadocorticoids

Answer 16

Stimulus for Release (what causes its release into blood):
Increased ACTH,

Effects:
Development of fetal testes (testosterone in man)
Development of secondary sexual characteristics,
Deepening of voice (male)
Facial and pubic hair (male)
Maintenance of estrogen effects after menopause.