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NE Exam 3 > Hypothalamic-Pituitary Relationships > Flashcards

Hypothalamic-Pituitary Relationships Flashcards

1
Q

What is the hypophysial stalk?

A

Physical connections between the hypothalamus and pituitary gland

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2
Q

What occurs with injury to the hypophysial stalk?

A

Oxytocin and vasopressin can still be released

Damage would prevent the release of hormones to the pituitary from the hypothalamus

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3
Q

Due to anatomical location tumors in the pituitary expand and put pressure on what?

A

The optic nerves

Visual problems and dizziness are often associated with pituitary tumors

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4
Q

The connection between the hypothalamus and posterior pituitary is what?

A

A neural signal

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5
Q

Describe the posterior pituitary

A

Derived from neural tissue
It is a collection of axons and nerve terminals whose cell bodies are located in the hypothalamus (includes the supraoptic nucleus and pareventricular nucleus)

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6
Q

What hormones are secreted by the posterior pituitary gland?

A

ADH (vasopressin) and oxytocin (neuropeptides)

Produced by cell bodies in the hypothalamus but released from the pituitary

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7
Q

What connects the anterior pituitary gland to the hypothalamus?

A

The hypothalamic-hypophysial portal blood vessels
Hormones move through the portal system to the anterior pit in high concentrations allowing for rapid response by the pituitary through the release of their own tropic hormones

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8
Q

What are the different hormone families?

A

ACTH family
TSH, FSH and LH family
GH and prolactin fam

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9
Q

What is the ACTH family?

A

Corticotrophs that secrete ACTH

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10
Q

What is the TSH, FSH and LH family?

A

Composed of two subunits: have the same alpha subunit in structure but differ in beta subunits
Thyrotrophs: secrete TSH
Gonadotrophs: secrete FSH and LH

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11
Q

What is the GH and prolactin family?

A

Somatotrophs: secrete GH
Lactotrophs: secrete prolactin
Very similar to each other in aa sequence

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12
Q

What is a primary endocrine disorder?

A

Associated with altered hormone levels due to defects in the peripheral endocrine gland (ex. Thyroid gland)

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13
Q

What is a secondary endocrine disorder?

A

Associated with altered level of hormones due to defects in the pituitary gland

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14
Q

What is a tertiary endocrine disorder?

A

Associated with altered levels of hormone due to defects in the hypothalamus

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15
Q

Describe the secretion of GnRH

A

Released from the hypothalamus in a pulsatile fashion which is necessary for the normal function of the gonadotropins and secretion of LH and FSH
Acts on gonadtrop cells in the ant pituitary

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16
Q

What is the role of LH and FSH in the testes?

A

LH stimulates Leydig cells for production of testosterone in testes
FSH acts on Sertoli cells and stimulates them to be responsive to androgens which aids in spermatogenesis

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17
Q

Describe the negative feedback that can occur from the testes

A

Sertoli cells secrete inhibin which inhibits LH and FSH from the ant pituitary
Testosterone has a negative feedback at the hypothalamus and ant pituitary decreasing LH (ant pituitary) or GnRH release (hypothalamus)

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18
Q

What is the role of LH and FSH in the ovaries?

A

LH acts on theca cells to produce androgens which are converted into estrogen in granulosa cells
FSH acts on granulosa cells to induce synthesis of estrogens which allow for follicle development

19
Q

Describe the negative feedback that can occur from the ovaries

A

Granulosa cells produce inhibin to regulate FSH levels from the ant pituitary
Progestins and estrogens can have negative feedback at the level of GnRH, FSH, and LH secretion
Mid cycle estrogen becomes a positive influence on hormone secretion

20
Q

What is acromegaly?

A

Rare disorder characterized by excess growth of ST, cartilage and bones in the face, hands and feet
Produces large thickened fingers/toes; hats, rights and shoes will feel too tight; gradual change in facial features
Due to excessive GH which can also decrease sensitivity of peripheral tissues to insulin and leads to an increase in blood glucose and produces compensatory hyperinsulinemia

21
Q

Describe the fluctuation of GH throughout the day

A

GH secretion fluctuates throughout the day with the highest secretion occurring during sleep
Sleep disturbances disturb GH secretion
Peaks with exercise (or even stress)

22
Q

Describe GH secretion throughout life

A

GH is secreted throughout life with a large spike during puberty and a decline shortly after
Stays constant throughout adult life and decreases in senescence

23
Q

What factors will stimulate release of GH?

A

Fasting/hunger/starvation, hypoglycemia, hormones of puberty, exercise, sleep and stress

24
Q

What are the direct actions of GH?

A

Stimulate response in bone and muscle, growth of cells (hypertrophy), increase in cell numbers (hyperplasia), increased cell metabolism (increase in glycogen and fat breakdown which allows for increased energy and protein synthesis)

25
Q

What are the indirect actions of GH?

A

Produces IGF-1 which effects almost every cell type in the body to cause proliferation and growth (hypertrophy and hyperplasia), and increase metabolic function of cells

26
Q

Gigantism occurs due to what?

A

Excess GH before closure of the bone epiphyses due to IGF1 stimulated long bone growth

27
Q

Acromegaly occurs with excess GH after what?

A

Closure of the bone epiphyses due to promotion of growth of deep organs and cartilaginous tissue

28
Q

Describe GH insensitive (a primary endocrine disorder)

A

Liver is not responsive to GH and an increase in GH levels occur
Prevents the production of IGF-1 which means it loses its negative feedback on GH
Feedback lost means hormone levels are not regulated
High GH, low IGF-1

29
Q

What will be seen with a secondary deficiency in GH?

A

GH is not being produced or released from pituitary gland

Results in decreased levels of IGF as well

30
Q

What will occur with a tertiary deficiency of GH?

A

GHRH is not being produced or released

Results in decreased levels of IGF as well

31
Q

Describe the effects of GH during the fed state

A

Fed state = increased carb intake meaning increased blood sugar and adequate insulin + increased protein intake meaning adequate aa availability —>
Liver will produce IGF-1 —> mitogenesis, lipolysis and cell differentiation

32
Q

Describe the effects of GH during unfavorable growth conditions

A

Unfavorable conditions = increased carb intake but decreased protein intake —> GH is inhibited and liver will not produce IGF-1 —> lipogenesis and carb storage —> weight gain

33
Q

Describe the effects of GH in a fasted state

A

Decreased carb and protein intake —> peripheral metabolism shifts to lipid as energy source —> GH levels increase and liver will produce IGF-1 —> lipolysis, ketogenic metabolism and diabetogenic
GH promotes lipolysis but can also promote insulin insensitivity
GH raises blood glucose by decreasing peripheral glucose uptake and stimulating hepatic gluconeogenesis

34
Q

What is the diabetogenic effect of GH?

A

Increase in blood glucose concentration which causes insulin resistance
Decreased glucose uptake and utilization by target tissues
Increased lipolysis in adipose tissue
Results in increased insulin levels

35
Q

What are some metabolic functions of GH?

A

Increased protein synthesis and organ growth through increased uptake of amino acids which stimulates synthesis of DNA, RNA and protein (mediated by somatomedins)
Increases metabolism of cartilage forming cells and chondrocyte proliferation (linear growth)

36
Q

IGF-1 can have a positive feedback effect on what?

A

GHIH

But negative on GH

37
Q

Describe the secretion of prolactin

A

Secreted by lactotrophs
Production and secretion highly associated with pregnancy
Secretion is pulsatile and is under tonic inhibition by dopamine

38
Q

What is the function of prolactin?

A

Mammary gland growth and stimulates/maintains production of milk in pregnancy and lactation

39
Q

What negative feedback effects can prolactin have?

A

Can have negative feedback effects on GnRH in the hypothalamus
Can cause lactational amenorrhea meaning women who are lactating have abnormal/absent menstrual cycles and it causes a decreased production of LH and FSH altering the follicle cycle

40
Q

How is oxytocin produced?

A

Produced as prepro-oxytocin in hypothalamus —> will be cleaved and packed into vesicles —> pro-oxyphysin —> travels down neuronal axon and becomes modified —> mature oxytocin by the time it reaches the pituitary
Stored in vesicles until it is reached

41
Q

What are the two major functions of oxytocin?

A

Milk ejection and uterine contraction

42
Q

Describe the effects oxytocin has on milk ejection

A

Milk let down: stimulates contraction of myoepithelial cells lining milk ducts
Major stimulus: suckling but also sight, sound or smell of an infant

43
Q

Describe the effects of oxytocin on uterine contraction

A

Stimulated by dilation of the cervix or orgasm

Creates positive feedback loop

NE Exam 3 (16 decks)

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