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renal and endocrine biology > Hypothalamus-Pituitary-Target Organ Axes: Feedback Control II > Flashcards

Hypothalamus-Pituitary-Target Organ Axes: Feedback Control II Flashcards

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1
Q

What is considered primary and secondary when discussing hypo and hyper secretory conditions in Anterior Pituitary Hormones?

A

Primary is the hypo or hypersecretion of the anterior pituitary cells

Secondary is the hypo or hypersecretion of the hypophysiotropic hormones

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2
Q

What is meant by hypophysiotropic hormones?

A

The secretory or inhibitory hypothalamus hormones such as GHIH

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3
Q

What is Panhypopituitarism?

A

It is the decrease in secretion in all anterior pituitary hormones

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4
Q

Panhypopituitary Dwarfism is associated with which group of individuals?

A

Children

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5
Q

True or False: The body’s physical parts develop in proportion to one another

A

In general, yes true

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6
Q

Discuss Panhypopituitary Dwarfism (3 sentences)

A
  • It is the deficiency of anterior pituitary hormones during childhood.
  • Rate of development of the individual is greatly decreased
  • Individual never passes through puberty as they never secrete sufficient quantities of gonadotropic hormones to develop adult sexual functions.
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7
Q

True or False: Panhypopituitarism in the adult and hypothyroidism are linked

A

True

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8
Q

Discuss Panhypopituitarism in the Adult (3 points)

A
  • It is the decreased secretion in all anterior pituitary hormones leading to hypothyroidism.
  • There is depressed production of glucocorticoids by adrenal glands => less cortisol
  • There is suppressed secretion of gonadotropic hormones leading to loss of sexual function
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9
Q

How is Panhypopituitarism in the adult treated?

A

It is treated with adrenocortical and thyroid hormones

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10
Q

True or False: The growth hormone is wholly responsible for determining the rate and final magnitude of growth

A

False: It is essential for growth but other hormones and genes are resposible for determining rate and final magnitude of growth

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11
Q

What are other growth-influencing hormones?

A

Thyroid hormone and sex hormones

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12
Q

Give 3 aspects that determine rate and final magnitude of growth

A

Genetic determination
Adequate diet
Freedom from chronic disease/stressful environment
Normal levels of growth-influencing hormones (such as thyroid hormone and sex hormones)

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13
Q

What is the most abundant hormone produced by the anterior pituitary?

A

Growth Hormone

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14
Q

At what ages do you expect the highest and lowest levels of growth hormone in the body? Give the approximate concentrations (just be close)

A

Highest levels from infancy to young adult (5-20) at 6 ng/ml

Lowest levels in late adulthood and elders (40-70) at 1.6 ng/ml

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15
Q

How is age related to GH secretion?

A

As age increases, secretion decreases

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16
Q

Once growth has ceased, are GH concentrations in the blood still significant?

A

Yes

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17
Q

Other than growth itself, what is another major effect of GH?

A

Metabolic Effects

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18
Q

What are the target organs that GH binds to in order to exert its metabolic effects?

A

Adipose tissue, skeletal muscles, and liver

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19
Q

What’re the effects of GH on adipose tissue?

A

Increases mobilization of fatty acids from adipose tissue => increasing fatty acids in the blood and increased use of fatty acids for energy.

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20
Q

What are the effects of GH on glucose in the body

A

GH decreases the rate of glucose utilization throughout the body => increasing blood glucose. This is done by decreasing muscle uptake of glucose which is important in conserving glucose for the brain.

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21
Q

What is the effect of GH on insulin

A

GH causes GH-induced insulin resistance

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22
Q

What are the effects of GH on the rate of protein synthesis?

A

Increases the rate of protein synthesis in most cells of the body

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23
Q

Metabolic disturbances due to excess GH secretion are very similar to what disease?

A

Type II diabetes

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24
Q

List the metabolic effects of GH on the body

A
  1. Increases mobilization of fatty acids from adipose tissue
  2. Decreases rate of glucose utilization throughout the body (decrease muscle intake and GH induced insulin resistance)
  3. Increases the rate of protein synthesis in most cells of the body
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25
Q

How does GH exert its growth-promoting effects?

A

GH does not act directly on its target cells. It enhances protein synthesis and bone growth.

GH exerts the majority of its growth-promoting effects indirectly by stimulating somatomedins

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26
Q

Give an example of somatomedins and give its structure and sources

A

Somatomedins are structurally and functionally similar to insuline. An example is IGF-1 or insulin-like growth factor 1.

The major source of circulating IGF-1 is the liver and is released into the blood on GH stimulation. It is also produced by most other tissues but only for local use and is not released into the blood.

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27
Q

Another name for IGF-1

A

Somatomedin C

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28
Q

Describe and Explain the effects of GH on bone growth

A

GH promotes growth of bone in length and thickness.

Length: Chondrocytes undergo cell division where older chondrocytes grow larger. Once older chondrocytes die, their matrix becomes calcified.

Thickness: Thickness increases by adding new bone on top of existing bone using osteoblasts. GH stimulates reproduction of these cells. Osteoclasts then remove older bone hence increasing thickness.

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29
Q

Explain the control of GH secretion

A

Hypothalamic Hypophysiotropic hormones such as GHRH and GHIH (Somatostatin). Increase and decrease secretion and synthesis.

Negative Feedback loops involving IGF-1 and GH. High blood levels of IGF-1 lead to decreased GH secretion by stimulating release of GHIH from the hypothalamus and hence suppressing somatotrophs in the anterior pituitary. GH inhibits GHRH and stimulates GHIH secretion.

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30
Q

Describe Diurnal rhythm as a factor influencing GH secretion

A

Diurnal rhythm is the Day/night rhythm of GH secretion. During most of the day, levels are fairly low and constant. Approximately 1 hour after onset of deep sleep, secretion increases (5x daytime values) and then rapidly drops over several hours

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31
Q

What are other factors (other than Diurnal Rhythm) influencing GH secretion

A

Think about the function of GH when remembering these
Exercise, stress, low blood glucose, increase in blood amino acids after a high protein meal, a decline in blood fatty acids.

Example: Remember that exercise, stress = low glucose in blood and GH conserves glucose levels in blood hence it is secreted

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32
Q

What are the causes of GH deficiencies and classify them as primary and secondary when applicable

A
  1. Hypothalamic dysfunction (secondary)
  2. Pituitary Defect (somatotrophs) (primary)
  3. Target Cells for GH fail to respond normally due to mutations in GH receptor
33
Q

True or False: Symptoms of GH Deficiencies are dependent on genetic predisposition

A

False They are dependent on age

34
Q

Hyposecretion of GH in children can lead to 3 conditions involving short stature. Name the 3 conditions.

A

Dwarfism
Laron Dwarfism
African Pygmies

35
Q

State the diagnosis of Laron Dwarfism

A

Normal GH blood levels but abnormal GH receptors on tissues

36
Q

State the diagnosis of African Pygmies

A

GH levels and target cell responsiveness normal but lack IGF-1

37
Q

How does the lack of IGF-1 affect GH activity

A

Deficient growth function of GH but metabolic function remains normal

38
Q

True or False: GH deficiency is more severe in adults than children

A

False, more severe in children

39
Q

Describe symptoms of GH deficiency in adults

A

Reduced skeletal mass and strength
Decreased bone density
Increased risk of heart failure

40
Q

Once insulin is released in the body, how does this affect GH levels. What is the response when GH deficiency is present?

A

Once insulin is released, this indicates that blood glucose levels were high and hence insulin drives glucose levels down. Low glucose levels stimulates GH secretion to conserve blood glucose => glucose levels increase. If there is deficiency then there is little to no response

41
Q

What can cause excess GH secretion? Give a primary and secondary cause

A

Tumor of somatotrophs in the anterior pituitary. (Primary)

Defect in the mechanisms regulating GH secretion (Hypothalamic Hypophysiotropic hormones) (secondary)

42
Q

True or False: Symptoms of excess GH secretion is also dependent on age

A

True

43
Q

True or False: Overproduction of GH in children can lead to increased risk of diabetes

A

True

44
Q

True or False: Increased production of GH in adults can increase risk of Hyperglycemia

A

True

45
Q

Give 1 symptom of excess GH production in children

A

Gigantism: Rapid growth in heigh without distortion of body proportions. Also increases risk of Hyperglycemia => Increased risk of diabetes

46
Q

Describe the effects/symptoms of excess GH secretion in adults

A

After adolescence, the person cannot grow taller but bones do become thicker causing Acromegaly.
Individuals may show increased thickening in extremities, face, hands, feet etc..
This can also lead to peripheral nerve disorders and insulin resistance => Hyperglycemia

47
Q

What term is associated to individuals that show bone thickening in their extremities and face.

A

Acromegaly

48
Q

A patient had their blood sampled before and after a glucose loading dose. What is expected to happen if it was a normal individual vs an individual with Acromegaly?

A

Normally, an increase in glucose should cause stimulation of GHIH to inhibit secretion of GH and hence there should be a decreased amount of GH.
If the patient with Acromegaly was sampled, then the decrease would not be significant hence confirming they have excess GH.

49
Q

How is a patient with excess GH treated?

A

Somatostatin mimetics (such as GHIH)

50
Q

Extended or excessive use of GH increases the likelihood of: Give 3 examples

A

Diabetes, kidney stones, high BP, joint pain, Carpal Tunnel Syndrome, Cancer

51
Q

Where is prolactin produced?

A

Anterior pituitary cells, lactotrophs

52
Q

State the role(s) of Prolactin

A

Stimulates breast development and milk production

Influences reproductive function and immune responses

53
Q

Under what state does prolactin secretion increase?

A

Pregnancy

54
Q

After delivery, when does prolactin levels fall?

A

3-6 weeks if no lactation and 8-12 weeks if suckling is maintained

55
Q

Describe the regulation of Prolactin secretion

A

There are two hypothalamic hypophysiotropic hormones; PIH/dopamine, and PRH

PRL also inhibits its own secretion via short-loop feedback by increasing synthesis and release of PIH

56
Q

State the Biological effects of Prolactin:

  1. Before and After Puberty
  2. During pregnancy
  3. Post-partum
A
  1. Stimulates proliferation and branching of ducts in female breast
  2. Causes development of lobules of alveoli within which milk is produced
  3. Stimulates milk synthesis and secretion
57
Q

State the role of prolactin in reproduction

A

Prolactin blocks synthesis and release of gonadotropic-releasing hormone hence preventing ovulation in women and sperm production in men

58
Q

Explain Prolactin’s role in immunity

A

Prolactin is synthesized by maternal uterine cells during pregnancy. This is important as it is required for acceptance of fetal tissue by mother and protection of maternal tissues from fetal invasion

59
Q

Give the symptom of prolactin deficiency

A

Inability to lactate in women

60
Q

Menses

A

Menstruation

61
Q

Give the symptoms of excess prolactin in:

  1. Women
  2. Men
  3. Both Sexes
A
  1. Infertility and loss of menses
  2. Decreased testosterone and sperm production. Increased breast development and lactation (rare)
  3. Libido Decreased (sex drive)
62
Q

What is the most common pituitary tumor and what does it lead to?

A

Lactotroph tumors, female infertility

63
Q

Prolactin has a similar ancestral origin to what other hormone?

A

GH

64
Q

What hormones are produced in the posterior pituitary? What type of hormones are they

A

Oxytocin and Vasopressin. They’re both peptide hormones

65
Q

What Hypothalmic nucleus produces Oxytocin; Vasopressin

A

Vasopressin is produced by the supraoptic nucleus and oxytocin is produced in the paraventricular nucleus

66
Q

State the functions of Oxytocin

A
  1. Causes milk ejection from lactating breast by contracting cells of the alveoli of the mammary gland
  2. Causes contraction of uterus during labor
67
Q

What is the function of Oxytocin in men?

A

No function/unclear function

68
Q

True or False: Milk ejection requires suckling of the infant to be ejected

A

True

69
Q

What stimulates oxytocin secretion and what type of regulation is that?

A

Secretion of oxytocin is increased by reflexes when infant suckers and within the birth canal during childbirth. This is an example of positive feedback

70
Q

What is another name for Vasopressin

A

ADH

71
Q

State the 2 functions of Vasopressin

A
  1. Retention of water by kidneys

2. Contraction of arteriolar smooth muscle (vasoconstriction)

72
Q

How is ADH secretion stimulated/inhibited?

A
  1. Water deprivation (Increased Osmolality of plasma and fluids bathing the brain). Water ingestion inhibits ADH
  2. Decreased blood volume or blood pressure stimulates ADH release.
73
Q

What are the receptors or sensors that fire for ADH?

A

Osmoreceptor for Osmolality

Baroreceptor for blood pressure/volume

74
Q

How and where is hypovolemia detected?

A

Hypovolemia is detected by pressure sensors of baroreceptors found in the walls of the left atrium and pulmonary veins known as the carotid and aortic baroreceptors.

75
Q

What is the relationship between age and ADH secretion

A

Older individuals secrete more ADH than younger individuals

76
Q

True or False: Pain, emotional stress, and Heat causes increased ADH secretion

A

True

77
Q

True or False: Ethanol or Alcohol is an inhibitor of ADH secretion

A

True

78
Q

Vasopressin deficiency leads to what disease most commonly?

A

Diabetes Insipidus

renal and endocrine biology (4 decks)

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