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Anterior pituitary function Flashcards

1
Q

Hypothalamic hormones - stimulating

A 
CRH
vasopressin
GnRH
GRH
Ghrelin
PRP, PRH
TRH
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2
Q

Hypothalamic hormones - inhibitory

A

Somatostatin

Prolactin inhibiting factors

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3
Q

CRH –> pituitary hormones

A

ACTH

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4
Q

Vasopressin –> pituitary hormones

A

beta lipotropin
beta endorphin
alpha MSH

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5
Q

GnRH –> pituitary hormones

A

LH

FSH

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6
Q

GRH –> pituitary hormones

A

Growth hormone

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7
Q

Ghrelin –> pituitary hormones

A

Growth hormone

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8
Q

Prolactin releasing prptides –> pituitary hormones

A

Prolactin

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9
Q

TRH –> pituitary hormones

A

TSH

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10
Q

Somatostatin –> pituitary hormones

A

INHIBITS growth hormone, thyrotropin, ACTH

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11
Q

Prolactin inhibiting factors –> pituitary hormones

A

Prolactin

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12
Q

Acidophil types

A

Mammosmmatotroph (GH, PRL)
Somatotroph (GH)
Lactotroph (PRL)

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13
Q

Basophil types

A

Corticotroph (ACTH, Endorphin, MSH, etc)
Thyrotroph (TSH)
Gonadotroph (LH, FSH)

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14
Q

GH effects

A

stimulates bone growth/protein synthesis
lipid/carb metabolism
synthesis of IGF1

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15
Q

Prolactin effects

A

lactation
testis and prostate: growth/development ???
Behaviour, immun

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16
Q

ACTH effects

A

stimulates production and secretion of GCs
stress response
homeostasis?

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17
Q

alpha-MSH effects

A

fetal growth??
skin pigmentation
inflammation

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18
Q

beta-endorphin effects

A

stress response???

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19
Q

TSH effects

A

stimulates production/secretion of thyroid hormones

thyroid growth

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20
Q

LH effects

A

ovulation
estrogen and progesternoe production
testis: development, testosterone synthesis

21
Q

FSH effects

A

testis: development, spermatogenesis
ovary: follicle maturation, estrogen production

22
Q

GH regulation

A 
\+GHRH: stress, exercise, sleep rhythms
\+GH: GHRH
-GH: somatostatin
GH on liver: IGF1 produced
IGF1 inhibits pituitary and hypothalamus
23
Q

Prolactin regulation

A

Breast suckling –> hypothalamus stimulated to produce TRH, PRPs?
Pituitary produces prolactin –> lactation
Prolactin stimulates hypothalamus

24
Q

ACTH/CRH regulation

A 
\+: stress
CRH/AVP stimulates ACTH production
ACTH on adrenal: cortisol
Cortisol inhibits pituitary and hypothalamus
ACTH inhibits hypothalamus
25
Q

TRH/TSH regulation

A

TRH –> pituitary makes TSH –> thyroid makes T3/T4

T3/T4 inhibits pituitary, hypothalamus

26
Q

FSH/LH regulation

A

Hypothalamus –> GnRH –> anterior pituitary produces LH, FSH

LH –> Interstitial cells makes testosterone –> testosterone inhibits hypothalamus and anterior pituitary

FSH acts on sertoli cells –> inhibin –> inhibits hypothalamus and anterior pituitary

27
Q

MOA of releasing and release inhibiting hormones

A

1) at anterior pituitary cells, act via binding to specific G-protein coupled 7 transmembrane spanning receptors (GPCRs)
2) GPCRs coupled to intracellular signalling pathways
3) All have a common final step: increased Ca, exocytosis

28
Q

Circadian rhythm

A

Diurnal
24 hour
e.g. cortisol, GH

29
Q

Ultradian rhythm

A

pulsatile
<24 hour
e.g. GH, LH, FSH
secreted hormones are directly responsible for specific events associated with physiological cycles
help avoid receptor desensitization and associated loss in responsiveness to a hormone

30
Q

Infradian rhythm

A

> 24 hour

e.g. menstrual cycle

31
Q

Circadian rhythm control

A

Suprachiastmatic nucleus of the hypothalamus
Intrinsic 24 hour cycle entrained with the light-dark cycle of the environment via direct and indirect input from the retina
Modification of the intrinsic cycle arise from the retina itself, the thalamus, mid-brain, hippocampus, and pineal gland

32
Q

Pituitary location

A

Inferior to the hypothalamus in the sella turcica (hypophysial fossa)
Covered by dura mater - sellar diaphragm

33
Q

Hypothalamus nuclei

A

Supraoptic nuclei –> ADH
Paraventricular nuclei –> ADH, oxytocin
Superchiastmatic nucleus –> Circadian rhythm

34
Q

Anterior pituitary cell types

A

Chromophil - acidophils (GH, PRL) basophils (ACTH, FSL, LH, TSH)
CHromophobes
Rudiments of Rathke’s pouch - colloid filled cysts

35
Q

Posterior lobe cell types

A

Pituicytes - like astrocytes in the CNS, nourishes neurosecretory axons
Herring bodies: stores granules at the terminal ends of axons

36
Q

Pituitary embryology

A

anterior from Rathke’s pouch, an invagination of oral ectoderm
Posterior from neuroectoderm, specifically, cells in the floor of the third ventricle

37
Q

Testosterone functions

A 
Growth of long bones during puberty
Muscle growth with puberty, increase in muscle strength
Stimulates red cell production
Stimulates prostate growth
Improves energy, cognition and mood
Libido, nocturnal erections
Growth of pubic, axillary, beard, chest, abdominal and back hair
Growth of larynx with voice deepening
38
Q

Sex hormone changes with age in men

A

Free and total testosterone decrease with age
70 yo: 66% of 30s
SHBG increases with age
DHEA decrease with age

39
Q

Sex hormone changes with age in women

A

Adrenal androgen production decreases from age 30-60, then ver slowly
SHBG increased in 60s and 70s
Reduction of adrenal precursors of testosterone may be more relevant to women because they account for at least 50% of testosterone activity in cells
Large variation in ovarian androgen production in the 50s and onwards

40
Q

Signs of testosterone deficiency

A

Early: fine body hair, smooth skin
Later: loss of body hair, softer beard, smaller and softer testes, small prostate, gynecomastia
Prolonged and severe: testes can become smaller and have a more rubbery consistency

Psychological: lack of energy, irritable mood, less assertive
Sexual: no nocturnal erections, loss of libido
Orgasms delayed with lower intesity, minimal ejaculate
(visually-induced erections are NOT dependent on testosterone)

41
Q

Testosterone replacement therapy risks

A

Men: CV harm when given to older men (many with chronic disease)

women: some women with high levels of androgen are prone to CV disease, insulin resistance and metabolic syndrome

42
Q

GH secretion characteristics

A 
large amount (0.4 mg)/day
high in newborns, tapers off in old age
pulsatile (episodic)
- most prominent during puberty
- amplitude and frequency regulated by the hypothalamus
43
Q

Involvement of Nor and Ach in GH response to hypoglycemia

A

GH secretion stimulated by deficiency of energy substrate
Glucose-sensitive central neurons activate GHR-secreting neurons in the arcuate nucleus, inhibit SS-secreting neurons in the PVN

44
Q

Involvement of Nor and ACH in GH response to sleep

A

Surge of GH secretion shortly after the onset of slow wave sleep
- men: nocturnal surge constitutes the bulk of GH secretion
- women: nocturnal surge constitutes only a fraction of GH secretion
Mechanism of surge unknown, but reduced cortisol, decreased SS secretion or hypersecretion of GHRH could all contribute

45
Q

GH feedback

A

short: hypothalamus: stimulate SS, inhibit GRH

Long: IGF1 stimulate SS, inhibit GRH, inhibit GH

46
Q

GH binding proteins

A

40-45% of circulating human GH bound to high-affinity glycoprotein
is the soluble form of the extracellular domain of the GH receptor
function: reduce rate of degradation of GH, acts as a reservoir for GH

47
Q

Jak-Stat system

A

JAK: janus kinase - tyrosine kinase
STAT - signal transducers and activators of transcription

1) absence of GH binding: receptor present as a dimer with JAK constitutively bound
2) GH binds to one molecule of the dimer, inducing the second receptor to bind to a different portion of GH
3) JAK molecules dimerize, cross phosphorylation of the JAK molecules (–> P JAK)
4) receptor tyrosines are phosphorylated by P-JAK
5) regions in the receptor phosphorylated by P-JAK are recognized by SH2-domains in intracellular signalling molecules, mosti mportantly STAT molecules. STATs phosphorylated by P-JAK

48
Q

IGF1

A

Production in liver stimultaed by GH
Muscle: increase aa transport, protein syntehsis
Adipose: increase lipolysis

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