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Endocrine & Reproductive Systems > L4 Hypothalamic Regulation of the Pituitary > Flashcards

L4 Hypothalamic Regulation of the Pituitary Flashcards

0
Q

What are corticotrophin-related peptides and what are the different types?

A
  • There are different types of corticotrophin-related peptides which are small peptide derived from the same common precursor (pro-opiomelanocortin)
  • They are: adrenocorticotrophic hormone, alpha-melanocyte-stimulating hormone, beta-lipocortin and beta-endorphin
  • alpha-MSH can be made too for intermediate lobe of pituitary gland in foetus
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1
Q

What are the three main types of anterior pituitary hormones?

A
  • corticotrophin related peptides
  • glycoproteins
  • somatomammotrophins
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2
Q

What are glycoprotein hormones?

A
  • compose of 2 different peptides but their alpha subunits are similar in structure; beta unit for each hormone differs and confers specificity
  • These are: LH, FSH and TSH
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3
Q

What does the term glycosylated mean?

A
  • adding a carbohydrate or sialic acid group.
  • the amount of carbohydrates and sialic acids determine the stability of the molecule, ie half life is longer when the molecule is MORE glycosylated = can prevent being degraded in blood
  • FSH is the most stable in blood, has the longest half life
  • chorionic gonadotrophin has similar structure too but it is not a pituitary gland hormone
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4
Q

What are somatomammotrophins?

A
  • single peptide chains with 2 or 3 disulphide bonds and with no carbohydrates
  • These are prolactin and growth hormones
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5
Q

What are the neurohypophysial hormones and what type of neurones are in charge of the release?

A
  • They are vasopressins and oxytocin, produced by magnocellular neurosecretory cells
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6
Q

What are the hypophysiotrophic hormones and where are they produced?

A
  • They are: thyrotrophin-releasing hormone, gonadotrophin-releasing hormone, somatostatin, growth hormone releasing hormone, prolactin-inhibiting hormone and corticotrophin-releasing hormone
  • they are being produced in parvocellular neurosecretory cells
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7
Q

Vasopressin and oxytocin (where are they being synthesised/ structures/ actions)

A
  • synthesised in supraoptic and paraventricular nuclei
  • have 9 amino acids, first 6 are identical for vasopressin and oxytocin= very similar structure
  • oxytocin is for milk ejection and expulsion of foetus at parturition; vasopressin is for anti-diuretics and regulate blood pressure long term
  • both can be found in parvocellular neurones too (so found in portal blood)
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8
Q

Corticotrophin- releasing hormone (where was it synthesised/ structure/ actions)

A
  • synthesised in paraventricular nucleus (parvocellular portion)
  • structure =41 amino acids
  • stimulate synthesis and release of ACTH from pituitary corticotroph cells
  • vasopressin (AVP) can be co-localised with CRH -> to potentiate corticotroph cells in releasing ACTH
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9
Q

Thyrotrophin-releasing hormone (where was it synthesised/ structure/ actions)

A
  • synthesised in paraventricular nucleus (parvocellular portion)
  • structure= tripeptide
  • to stimulate synthesis of TSH from pituitary thyrotroph cells
  • high level of TRH also stimulates release of prolactin
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10
Q

Gonadotrophin-releasing hormone (where was it synthesised/ structure/ actions)

A
  • synthesised in arcuate nucleus
  • structure: decapeptide
  • to stimulate synthesis and release of FSH and LH from pituitary gonadotroph cells
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11
Q

Growth hormone-releasing hormone (where was it synthesised/ structure/ actions)

A
  • synthesised in arcuate nucleus
  • structure= 44 amino acids
  • stimulate synthesis and release of GH from pituitary somatotroph cells
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12
Q

Somatostatin (where was it synthesised/ structure/ actions)

A
  • synthesised in periventricular nucleus
  • structure= tetradecapeptide
  • inhibits synthesis and release of GH from pituitary somatotroph cells
  • also inhibits release of TSH
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13
Q

What is octreotide?

A
  • a synthetic analogue of somatostatin
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14
Q

Prolactin-inhibiting hormone dopamine (where was it synthesised/ structure/ actions)

A
  • synthesised in arcuate nucleus
  • tuberoingundibular dopamine neurones project to median eminence in hypothalamus
  • structure: monoamine (the only monoamine hormone that is produced in hypothalamus)
  • acts to inhibit synthesis and release of prolactin from pituitary lactotroph cells
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15
Q

What is bromocriptine?

A
  • a dopamine agonist so can act as prolactin-inhibiting hormone dopamine to inhibit synthesis and release of prolactin
16
Q

What are the different signals that can act on the regulation of hypothalamic neurosecretory cells?

A
  • CSF signals, cireumventricular organs, neural signals, blood signals
  • so can encourage the release of hypothalamic hormones into blood
17
Q

What is a short loop feedback?

A
  • it is where feedback occurs at pituitary level and feeding back to hypothalamus
18
Q

Why there is only a small amount of hypothalamic hormones needed to act on pituitary?

A
  • Because it works via the cascade with amplification and also it only needs a minute amount travelling in portal blood for causing effects in pituitary
19
Q

What would occur if there is an over/underproduction of CRH/ ACTH?

A
  • overproduction = cushing’s disease/ syndrome
  • underproduction = addison’s disease
  • this axis could be disturbed under stress and at its highest in mornings
20
Q

What would occur if there is an over/underproduction of TRH/ TSH?

A
  • overproduction: Grave’s disease

- underproduction: hypothyroidism

21
Q

What would occur if there is an over/underproduction of GnRH/ LH & FSH?

A
  • stress, poor nutrition, extreme level of exercise and day length can reduce the production of these hormones
  • underproduction = Kallmann’s syndrome
22
Q

What would occur if there is an over/underproduction of GhRH/ GH?

A
  • overproduction in children before epiphyseal fusion = gigantism; in adults = acromegaly
  • underproduction = failure to grow
  • this axis could be altered with stress, sleep, exercise
23
Q

What would occur if there is an over/underproduction of Dopamine/ PRL?

A
  • overproduction = can lead to infertility as it has an inverse relationship with GnRH
  • suckling can increase prolactin level while stress can reduce it
24
Q

What are the causes of pituitary disorders?

A
  • hypersecretion: functioning tumours ( producing prolactin/ GH are most common)
  • hyposecretion: craniopharyngeoma, non-functioning pituitary tumours, radio/chemotherapy, trauma, empty sella syndrome
25
Q

What are the replacement therapy for hypopituitarism for different hormones?

A
  • GH: synthetic GH
  • ACTH: treatment with hydrocortisone/ prednisolone
  • TSH: treatment with L-thyroxine
  • FSH/ LH: treatment with oestrogen/ progesterone in women ; testosterone in men
  • AVP: treatment with desmopressin by nasal insufflation or tablets
26
Q

What would prolactin inhibit?

A
  • prolactin is produced when women are lactating so it naturally inhibits FSH/LH to prevent further release of eggs. = can’t be pregnant

Endocrine & Reproductive Systems (11 decks)

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