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medicine > WEEK 7: 7.5 Growth Hormones and Gonadotropins > Flashcards

WEEK 7: 7.5 Growth Hormones and Gonadotropins Flashcards

1
Q

What cells synthesize and secrete growth hormones

A

somatotrophs

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2
Q

what two hypophysiotropic hormones regulate secretion of growth hormones in the anterior pituitary gland?

A

growth hormone releasing hormone & growth hormone inhibiting hormone

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3
Q

what is the primary target of growth hormones?

A

the liver, where it stimulates the release of an insulin like growth factor (IGF)

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4
Q

Define growth

A

the progressive increase in the size of a living organism that requires the net synthesis of proteins

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5
Q

What does growth elongate?

A

the long bones and the size/no of cells in soft tissues

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6
Q

What factors influence growth?

A

genetics, nutrition, growth influencing hormones, stress and disease

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7
Q

What factors influence fetal growth

A

Placental hormones
birth size (genetics/environment)
neurological growth

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8
Q

What factors influence postnatal growth

A
  • growth hormone, somatomedins, T3 and T4, insulin, androgens and estrogens
  • increased growth hormones during puberty
  • increased androgens contribute to pubertal growth spurt
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9
Q

How do sex steroids like androgens increase growth

A

they stimulate protein synthesis and have permissive interaction with GH

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10
Q

how can insulin affect growth?

A

excess insulin can stimulate excessive growth whilst a deficiency can block growth

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11
Q

how does the thyroid hormone affect growth?

A

hypothyroidism can stunt growth while hypersecretion of thyroid hormone does not stimulate excess growth

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12
Q

what is a growth hormone

A

a peptide hormone produced by somatotrophs of the anterior pituitary

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13
Q

what is the secretion of growth hormones regulated by

A

hypophysiotropic hormones GHRH and GHIH (aka somatostatin)

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14
Q

If you were to track GH during sleep, what would you see?

A
  • irregular pulses
  • larger bursts during deep sleep
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15
Q

What are major positive stimuli for GH release?

A
  • exercise
  • stress
  • hypoglycemia
  • fasting
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16
Q

What regulates growth hormone secretion?

A
  • GH inhibits GHRH and stimulates GHIH
  • IGF inhibits somatotrophs and hence reduces GH
  • IGF stimulates GHIH release
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17
Q

What is the primary target of growth hormones?

A

the liver

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18
Q

What is one of the main responses to GH receptor activation in the liver?

A

the release of IGF-1/somatomedin

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19
Q

What promotes the growth of bones in the soft tissues during childhood and adolescence?

A

IGF-1 binding to its receptors

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20
Q

define the term somatomedins

A

they are peptide hormones that have strong mitogenic (encouraging cell division) properties

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21
Q

Where are somatomedins primarily produced

A

in the liver but also in other tissues

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22
Q

What are the two types of somatomedins?

A

IGF-1
IGF-2

23
Q

What effect does IGF-1 have?

A

it stimulates cell growth, multiplication and inhibits apoptosis

24
Q

What is IGF-2

A

a growth promoting hormone during gestation

25
What cell signaling pathway do growth hormone receptors activate?
JAK/STAT
26
What are the 3 important components of JAK STAT signaling receptors
1. the receptor protein itself, which binds the primary messenger such as the growth hormone, JAK enzymes, and a protein which serves as a signal transducer and activator of transcription
27
What does binding of growth hormones to its receptor cause?
the phosphorylation and activation of the stat protein, which in turn, activates gene transcription to synthesise protein
28
What is the overall effect of growth hormone?
promote protein synthesis, use fat stores but also promote hyperglycemia
29
What effect does IGF-1 have on the proliferation of periosteal osteoblasts and bone remodeling
it increases both of these
30
What effect does IGF-1 have on cell size and number?
increases cell size and cell number
31
What other effects does IGF-1 have on proliferation of epiphyseal cartilage and conversion of cartilage to new bone
it stimulates the proliferation of epiphyseal cartilage and increases conversion of cartilage to new bone
32
Define gonadotropin
the collective name for follicle stimulates hormone and luteinizing hormone, which are secreted from the gonadotropin cells of the anterior pituitary
33
What do gonadotrophs produce in the anterior pituitary
Lutenising hormone (LH) and follicle stimulating hormone (FSH)
34
What is the primary function of LH and FSH?
they act on gonadotrophs by activating cAMP cell signalling pathways in the ovaries and testes to stimulate gameete development, as well as stimulate the synthesis of estrogen and progesterone in the ovaries and testosterone in the testes
35
What role does LH play in males?
it acts primarily on the leading cells in the testes, where is stimulates testosterone synthesis and secretion
36
How does FSH also promote sperm production?
it stimulates the production of cell products in the search cells that exert direct effects both on sperm development and maturation
37
What does an acute surge of LH do in females
stimulates ovulation
38
What role does FSH play in females
it promotes follicle development, induces LH receptors on dominant follicle and stimulates estrogen secretion from follicles
39
What occurs to females in the early to mid-follicular phase?
FSH stimulates the growth of ovarian follicles and oocyte maturation, follicles secrete more estrogen, causing rising, moderate levels of estrogen.
40
What does the rising moderate levels of estrogen in the early to mid-follicular phase cause
- selective inhibition of FSH secretion as well as inhibition of GnRH secretion - promotes proliferation of the endometrium
41
What occurs in the late follicular phase and ovulation?
- Inhibin inhibits FSH secretion from pituitary - High levels of estrogen triggers a LH surge - LH surge triggers the re-initiation of oocyte meiosis, local prostaglandin production and luteinization of follicular cells to luteal cells
42
What occurs in the early to mid luteal phase?
- LH causes differentiation of thecal and granulosa cells into luteal cells of the corpus luteum -Corpus luteum secretes progesterone, estrogen and inhibin
43
What does progesterone do in the early to mid luteal phase?
- exerts negative feedback on the hypothalamus and anterior pituitary - stimulates secretory changes in the endometrium -thickens cervical mucus - exerts thermogenic activity
44
What occurs in the late luteal phase if there is no pregnancy?
If there is no pregnancy, deterioration of the corpus luteum causes progesterone to decrease. endometrial necrosis increases menses, as lining is shed, surface epithelium is already regenerating. With progesterone levels declining, FSH can start to rise again, initiating a new cycle.
45
What occurs in the late luteal phase if there is pregnancy ?
maintain increased progesterone, estrogen and inhibin
46
What are the 3 phases of the uterine cycle?
- proliferative phase - secretory phase - menstrual phase
47
what occurs in the proliferative phase?
endometrium repaid and proliferation under influence of estrogen from newly growing follicles
48
What occurs in the secretory phase?
Progesterone converts endometrium to highly vascularised tissue and endometrial glands secrete glycogen and mucus
49
What occurs in the menstrual phase?
the uterine prostaglandins increase vasoconstriction, contractions and cramping, discharge of blood and endometrial debris
50
What does hypersecretion of GH during childhood cause
the body remains in proportion- gigantism
51
What does hypersecretion of GH after adolescence cause?
the bones cannot lengthen, causing acromegaly
52
What are the causes, effect and treatment of gigantism?
cause- pituitary adenoma, pituatary hyperplasia effect- rapid growth of all tissues, hyperglycemia (leading to diabetes mellitus) treatment: somatostatin analogs, surgery
53
What are the causes, effect and treatment of acromegaly?
cause: pituitary tumor after adolescence effect: bones grow in thickness not length, enlargement of hands and feet, elongation of ribs, enlarged tongue, liver, kidneys, heart. Diabetes treatment: somatostatin analogs, surgery

medicine (52 decks)

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