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Endo/Repro Midterm > Hypothalamic-Pituitary Relationships > Flashcards

Hypothalamic-Pituitary Relationships Flashcards

1
Q

What is one of the first symptoms that occurs when you have a problem with your hypothalamus?

Why?

A

Visual problems

Pituitary gland is encased in bone; if a tumor or problem occurs, it goes up into the brain and compress the optic N lies

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2
Q

Hypothalamus is broken into smaller ____ with _____.

A

Nuclei with cell bodies

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3
Q

Communications between the anterior pituitary gland and the hypothalamus are ____, ____, and ____.

Neural signals synapse on ____.

Connected to hypothalamus by the ___.

A

Neuronal, hormonal, vasculature

Vasculature bed

Hypophysial portal system

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4
Q

Anterior pituitary secretes what hormones?

A 
ACTH
TST
FSH
LH
GH
Prolactin
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5
Q

_____ can be directly delivered to the anterior pituitary gland.

They do not appear in ____ concentration in systemic circulation.

A

Hormones

High

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6
Q

A collection of axons whose cell bodies are located in the hypothalamus and extend into the ____.

What are the cell bodies in the hypothalamus called?

What does it secrete?

A

Posterior pituitary gland

Supraoptic nucleus (SON)

Paraventricular nucleus (PVN)

ADH (SON)
Oxytocin (PVN)

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7
Q

Communication between the hypothalamus and posterior pituitary is a _____ signal.

Communication between the hypothalamus and anterior pituitary is _____ communication.

A

Neuronal

Hypothalamic-hypophysial portal system (vascular)

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8
Q

Abnormal amounts of a hormone can be due to a dysfunction at different levels of the endocrine axis.

What are the levels and where do they come from?

A

Tertiary endocrine disorder: hypothalamus

Secondary: pituitary gland

Primary: peripheral gland

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9
Q

Hormones of the anterior pituitary are organized into families by structure and function. What hormones are in each family and where are they secreted from?

ACTH family?
TSH, FSH, LH family?
GH, prolactin family?

Hypothalamus -> target in anterior pituitary -> hormone

A

CRF -> Corticotrophs secrete ACTH

TRH -> Thyrotrophs secrete TSH
GnRH -> Gonadotrophs secrete FSH and LH

GHRH stimulates ;somatostatin (GHIH) inhibits-> Somatotrophs secrete GH
PIF (dopamine) inhibits; elevated TRH stimulates -> Lactotrophs secrete prolactin

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10
Q

What drives endocrine relationships?

This activity is maintained at a ___ point.

Hypothalamic neurons are secreted in a _____ manner to a _____ rhythm (secreted up and down)

A

Axes

Set

Pulsatile

Circadian

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11
Q

What are the anterior pituitary gland axes? (6)

A

Hypothalamic-pituitary-gonad (HPG)

Hypothalamic-pituitary-liver

Hypothalamic-pituitary-prolactin

Hypothalamic-pituitary-reproductive (testis/ovaries)

Hypothalamic-pituitary-thyroid

Hypothalamic-pituitary-adrenal

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12
Q

Disease characterized by excessive growth of soft tissue, cartilage, and bone in the face, hands, and feet and develops gradually

What causes this?

Symptoms?

A

Acromegaly

Prolonged and excessive secretion of GH in adult life

Prominent supraorbiral ridges
Organomegaly
Hyperglycemia
Lower teeth separation
Prominent lower jaw
Enlarged head
Mental disturbances 
Accelerated osteoarthritis
Hypertension
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13
Q

GH or somatotropin is produced by ____ in _____.

Targets ____ and ___.

GH receptor linked to ____ signaling.

Inhibited by ____.

A

Somatotropes; anterior pituitary

Liver and bone

JAK-STAT

Somatostatin (GHIH) and IGF-1 (insulin related growth factor 1; part of the negative feedback)

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14
Q

How does GH target the liver?

How does this negative feedback to GH secretion?

A

Causes the liver to release IGF-1, which can target the bone, muscle, skin

IGF-1 inhibits GH secretion (negative feedback)

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15
Q

What stimulates GH?

A 
Fasting/hunger/starvation
Hypoglycemia
Exercise
Sleep
Stress
Hormones of puberty
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16
Q

What are the direct actions of GH?

A

Growth: hypertrophy (increase size/volume of cells)

Cell reproduction: hyperplasia (increase number of cells)

Metabolism: increases glycogen and fat breakdown for energy; increases protein synthesis

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17
Q

What are the indirect actions of GH?

A

Tropic function

Signals liver to produce IGF (insulin-like growth factor)

IGF Stimulates hypertrophy and hyperplasia

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18
Q

Explain the three levels of the hypothalamic-pituitary-growth hormone axis

A

Hypothalamus: GHRH, GHIH (somatostatin)

Anterior pituitary: GH (somatotropin)

Liver: IGF, IGF-1 (somatomedin C)

**Gastric fundal cells: secrete ghrelin to stimulate GH release

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19
Q

Explain the hypothalamic-pituitary-growth hormone axis (HPGh) and its use of negative feedback

A

IGF-1 can inhibit the release of GH from the anterior pituitary or stimulate the release of GHIH from the hypothalamus

GH can inhibit the release of GHRH from the hypothalamus

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20
Q

Gigantism caused from excess ___.

Gigantism occurs ____ closure of bone epiphyses due to excess stimulation of long bone growth by ____.

Acromegaly occurs ____ closure of bone epiphyses due to promotion of growth of _____.

A

Growth hormone

Before

IGF-1

After

Deep organs and cartilaginous tissue

21
Q

What are growth promoting factors during a fed state?

This causes the liver to do what?

A

Increase carb intake and increase blood sugar cause adequate insulin availability
AND
Increase protein intake causes adequate AA availability

Both cause liver to produce IGF-1 causing mitogenesis, lypolysis, differentiation

22
Q

What are unfavorable growth conditions during a fed state?

This causes inhibition of what?

Casing the liver to do what?

A

Adequate carb and blood sugar levels but decreased protein intake and inadequate AA availability

Therefore GH is inhibited

Liver doesn’t produce IGF-1 -> lipogenesis and carb storage (weight gain)

23
Q

What causes growth factors to shift in the fasting state?

What does peripheral metabolism shift to?

This causes the increase of what?

Causing the liver to do what?

A

Low carb intake, hypoglycemia, inadequate insulin availability but high protein intake and adequate amino acid availability

Shifts from carbs to lipids as an energy source

Increase GH levels

Liver produce IGF-1 -> lipolysis, ketogenic metabolism, diabetogenic (can result in insulin insensitivity)

24
Q

Metabolic fx of GH

A

Diabetogenic effect (increase blood sugar): causes insulin resistance, decrease glucose uptake, increase lipolysis, increase blood insulin

Increase protein synthesis and organ growth: increase uptake of AA, stimulates synthesis of DNA, RNA, protein; mediated by somatomedins (IGF-1)

Increase linear growth: stimulates synthesis of DNA, RNA, protein; mediated by somatomedins, increase metabolism in cartilage-forming cells and chondrocytes proliferation

25
Q

When is the biggest secretion of GH?

A

During sleep

During puberty

Peaks with exercise

26
Q

What causes GH deficiency?

GH excess?

A

Decrease secretion of GHRH, decrease GH secretion, failure to generate somatomedins, GH or somatomedin resistance (deficiency of receptors)

GH-secreting adenoma, gigantism before puberty, acromegaly after puberty

27
Q

How do you diagnose acromegaly?

A

GH and oral glucose tolerance test

When given oral glucose, pt’s secretion of GH should be inhibited; but in pt with acromegaly GH is not suppressed

Failure to suppress serum GH leads to IGF-1 levels remaining constant throughout the day

Pituitary enlargement on MRI

28
Q

Tumor causing excessive hormone production from pituitary gland

Examples?

A

Pituitary adenoma

Prolactinoma (most common)
Acromegaly/gigantism
Cushing’s disease

29
Q

What secretes prolactin? From what?

When does secretion begin?

What kind of secretion?

What inhibits it?

Action?

A

Lactotropes; anterior pituitary

5th week of pregnancy

Pulsatile

Under tonic inhibition by hypothalamic dopamine

Stimulate and maintain lactation; suppresses GnRH (inhibit LH and FSH) to decrease reproductive fx and suppress sexual drive

30
Q

Stimulators of prolactin secretion

Inhibitors of prolactin secretion

A

Pregnancy (estrogen), Brest-feeding, sleep, stress, TRH

Dopamine, dopamine agonists, somatostatin, prolactin by negative feedback

31
Q

Describe the three levels of the prolactin cascade

A

Hypothalamus: TRH, dopamine (inhibits)

Anterior pituitary: prolactin

Mammary glands: Lactation

32
Q

FDH and LH secreted by what? From?

Action?

What regulates secretion?

A

Gonadotropes; anterior pituitary

Estrogen and progesterone secretion in females for normal menstruation; testosterone production in males

Hypothalamic GnRH (GnRH can be inhibited by energy deficits, anorexia, extreme exercise, depression)

33
Q

Hyperprolactinemia suppresses what hormones that act on what organ?

How?

Symptoms of excess prolactin?

A

FSH and LH; ovaries

Prolactin inhibits GnRH from hypothalamus -> inhibits secretion of FSH and LH from anterior pituitary

Galactorrhea, infertility

34
Q

What causes hypopituitarism?

A

Brain damage
Pituitary tumor (adenoma)
Non-pituitary tumor (craniopharyngioma most common)
Infections (meningitis, encephalitis, hypophysitis)
Infarction (Sheehan syndrome: the pituitary is in larger during pregnancy)
Autoimmune disorders
Pituitary hypoplasia
Genetic disorders

35
Q

Disease when the pituitary is enlarged and more vulnerable to infarction during pregnancy

Causes hypopituitarism

A

Sheehan syndrome

36
Q

Disease causes by lack of effect of ADH on renal collection duct

Results in polyuria

What is the normal function of ADH?

A

Diabetes insipidus (DI)

Normally ADH induces permeability of the renal collecting duct so it absorbs water

In DI, water is not absorbed, therefore polyuria, dilute urine

37
Q

Symptoms of diabetes insipidus

What are the two types of DI?

A

Polyuria, polydipsia, polyphagia

Central: deficient secretion of ADH from hypothalamus or pituitary

Nephrogenic: renal insensitivity to ADH

38
Q

How do you diagnose diabetes insipidus?

What differentiates between central and nephrogenic DI?

A
  1. WATER DEPRIVATION TEST: to assess the ability of the pt to concentrate urine when fluids are withheld

Drink normal fluids, obtained baseline urine osmolality, withhold water and measure osmolality, administer desmopressin and measure osmolality

Normal function: urine will concentrate
Diabetes insipidus: urine will stay diluted even when dehydrated
Central DI: urine will concentrate when desmopressin is given (kidneys work)
Nephrogenic: urine will stay diluted with desmopressin

  1. ADH TEST to differ between central and nephrogenic DI: Test urine output, challenge with ADH, retest urine output

Central: kidneys respond by concentrating urine, problem with brain
Nephrogenic: kidneys can’t concentrate urine, problem with kidneys

39
Q

Types of DI:

Lack ADH, decrease plasma ADH, damage to posterior pituitary or hypothalamus; desmopressin test successful

Kidney unresponsive to ADH, increase plasma ADH, chronic kidney disease, lithium toxicity; desmopressin test unsuccessful

A

Central DI

Nephrogenic DI

40
Q

Disease causing excess secretion of ADH, excessive water retention, hyponatremia

Hypoosmolarity fails to inhibit ADH release

Explain hyponatremia

A

SIADH

Hyponatremia is caused by ADH induced water retention; the high volume activates secondary natriuretic mechanisms (aldosterone) that cause Na and water loss; net effect with chronic SIADH is Na loss is more prominent than water retention

41
Q

What hormones do the posterior pituitary gland secrete?

A

Oxytocin and ADH

42
Q

What are the two actions of oxytocin?

How are these actions stimulated?

A

Milk ejection: stimulates contraction of myoepithelial cells lining milk ducts
Stimulated by suckling, sight, sound, smell of infant

Uterine contractions: stimulated by dilation of cervix or orgasm; pitocin (induction of labor)

43
Q

Summary of the control of the hypothalamic-anterior pituitary hormones

A

CRH -> increase ACTH, MSH

Dopamine -> decrease prolactin

GHRH -> increase GH

GnRH -> increase FSH, LH

Prolactin -> decrease GnRH (leading to decrease FSH/LH)

Somatostatin -> decrease GH, TSH

TRH -> increase TSH, prolactin

44
Q

Explain GH insensitivity

What kind of deficiency is it?

A

Primary deficiency because problem with gland

GHRH is released from the hypothalamus, causes GH secretion from the anterior pituitary

However, during GH insensitivity, the LIVER will not respond to GH, therefore IGF will not be secreted

More GH is secreted because more is needed to induce a response from the liver

45
Q

Explain a secondary GH deficiency

Tertiary deficiency of GH

A

GHRH is secreted from the hypothalamus but the anterior pituitary does not respond and GH levels don’t rise; IGF not secreted

GHRG is not secreted from the hypothalamus so no signal is relayed

46
Q

How do you diagnose acromegaly?

A

Elevated serum GH and IGF-1 levels

AND

Failure to suppress GH production in response to oral load of glucose test

(high amounts of sugar should feedback and inhibit GH secretion; but if that fails, and has elevated GH and IFG-1, pt could have acromegaly)

47
Q

What do estrogen and testosterone inhibit in their feedback mechanism?

What also alters FSH release?

A

They inhibit the release of FSH and LH from the anterior pituitary

Estrogen feedback depends on menstrual cycle

Ovaries also secrete inhibit and activin that alter FSH release

48
Q

Compare the mechanisms and causes of euvolemic and hypervolemia hyponatremia

A

Euvolemic: extracellular Na normal, TBW increased

Causes: SIADH, COPD, malignancy

Hypervolemia: extracellular Na increased, TBW greatly increased

Causes: CHF, renal impairment, cirrhosis

49
Q

Compare SIADH to DI

A 
Urine output: low, high
ADH: high, low or normal
Plasma Na: low, high
Hydration status: high, low
Thirst: high, high
Body water content: normal or high, low

Endo/Repro Midterm (11 decks)

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