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The Patient Y3 semester 1 > Hypothalamic & Pituitary Hormones (plus Pineal gland) > Flashcards

Hypothalamic & Pituitary Hormones (plus Pineal gland) Flashcards

1
Q

Where is the hypothalamus located and what is It important for?

A

• Located below the thalamus, just above the brain stem.
• Important for the control of basic functions such as hunger, thirst, sleep.
- Senses internal and external environment.

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2
Q

Where is the pituitary gland located?

A

• Sits in a small bony cavity, below the hypothalamus - sella turcica

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3
Q

How big is the pituitary gland?

A

• Size of a pea and weighs ~0.5 g

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4
Q

What is the name of the stalk that connects the pituitary gland to the hypothalamus?

A

The infundibulum/pituitary stalk

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5
Q

What is the name of the two lobes in the pituitary gland?

A
  • Anterior - Parvicellular neurons
  • Posterior - Magnocellular neurons

These link to the hypothalamus in very different ways.

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6
Q

Describe the anterior (parvicelllar) neurones:

A

They secrete regulatory hormones into the bloodstream which travel through the portal system to the anterior pituitary lobe triggering secretion of other hormones (circulatory system link)

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7
Q

Describe the posterior (magnocellular) neurones:

A

Magnocellular neurons in the hypothalamus have long axons which extend down into the posterior pituitary lobe (direct neuro-endocrine link).

(Magno means large)

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8
Q

The anterior pituitary does NOT have a direct nervous connection with the hypothalamus. True or false?

A

True

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9
Q

The hypothalamus exerts control of the anterior pituitary by __________________.

A

Secreting regulatory (releasing and inhibitory) hormones

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10
Q

Name the hypothalamic (regulatory) hormones?

A
  • Follicle Stimulating hormone (FSH) (tropic)
  • Luteinising Hormone (LH) (tropic)
  • Adrenocorticotropic hormone (ACTH) (tropic)
  • Thyroid Stimulating Hormone (TSH) (tropic)
  • Prolactin (PRL) (non tropic)
  • Growth Hormone (GH) (non tropic)

FLAT PiG

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11
Q

What does tropic mean?

A

Means that that hormone will act on an endrocrine gland to cause the release of an another

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12
Q

What is the alleged effect of the release of Prolactin Releasing Hormone?

A

Mammary development and lactation.

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13
Q

What is Prolactin Inhibiting Hormone also known as?

A

Dopamine

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14
Q

Anterior pituitary and effect of PIH?

A

None - non tropic

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15
Q

Anterior pituitary for and effect of Thyrotropin Releasing Hormone?

A

Thyroid stimulating hormone (TSH) and secretion of thread hormones by thyroid gland.

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16
Q

Anterior pituitary for and effect of corticotropin releasing hormone (CRH)?

A

Adrenocorticotropic hormone (ACTH) and adrenal cortex.

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17
Q

Anterior pituitary for and effect of Growth Hormone Releasing Hormone.

A

Growth hormone.

Effect - growth and secretion of insulin like growth factors from liver.

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18
Q

Anterior pituitary for and effect of Growth Hormone inhibiting Hormone (GHIH)

A

Non tropic

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19
Q

Anterior pituitary for Gonadotropin releasing hormone (GNRH) and effect .

A 
AP = FSH and LH 
Effect = Gonads for production of sex hormones
20
Q

What do the tropins (FLAT) do?

A

regulate the function of other primary endocrine glands to produce effector hormones

21
Q

Function of FSH (Gonadotropin) and LH (Gonadotropin)?

A
  • Synthesised, stored & secreted from gonadotropes
  • FSH stimulates ovaries to produce estrogen & testes to produce testosterone
  • LH has a role in ovulation and the growth of the corpus luteum
  • LH stimulates androgen secretion by interstitial cells in testes
22
Q

Function of ACTH (Corticotropin)?

A
  • Synthesised, stored & secreted from corticotropes

* Stimulates the adrenal gland cortex to produce corticosteroids such as aldosterone and cortisol

23
Q

Function of TSH (thyrotropin)?

A
  • Synthesised, stored & secreted from thyrotropes

* Stimulates the thyroid gland to produce thyroid hormones such as T3 and T4 (thyroxine)

24
Q

What are the non tropic hormones?

A

Prolactin and Growth Hormone (GH) (PiG) act directly on other tissues.

25
Q

Function of prolactin?

A
  • Synthesized, stored, & secreted by lactotropes
  • Roles and functions complex
  • includes effects on breast tissue for lactation
  • Dysregulation causes multiple problems
  • Most common pituitary tumour is prolactinoma (tumour in lactotrope cells)
  • Treated using dopamine receptor agonists
  • e.g. bromocriptine, cabergoline
26
Q

Function of growth hormone?

A
  • 191-amino acid, single-chain polypeptide
  • Synthesized, stored, & secreted by somatotropes
  • Stimulates growth, cell reproduction and regeneration of specific cells
  • Hypersecretion of growth hormone causes gigantism (before long bones has fused) in children and acromegaly in adults.
27
Q

What is Acromegaly?

A

Acromegaly - enlargement of the head, hands, feet, lower jaw, tongue and lips
excessive sweating, headaches and visual field loss, due to pressure on optic nerve (where pituitary is located)

28
Q

How is acromegaly treated?

A
  • Hard to get to pituitary for surgery so drug treatment used
    • Somatostatin (growth hormone inhibiting hormone GHIH)
    cf somatotropin (GH) – do not confuse the terminology!
  • Regulates production of growth hormone (GH) AND affects cell proliferation & growth via somatostatin receptors
  • Synthetic analogues have much longer half-life
  • Sandostatin has only 8 AA and a 90 mins half-life vs 3 mins for endogenous ligand
  • Somatostatin 14 amino acids
29
Q

What is growth hormone deficiency also known as?

A

Pituitary dwarfism

30
Q

How does Insufficient growth hormone production occur?

A
  • Hypothalamic or pituitary tumor (tumor presses on stalk that connects hypothalamus and pituataryy gland preventing signals getting to the hypothalamus preventing secretion of growth hormone0
  • (craniopharyngioma most common)
  • Mutation of GH genes
  • Head injury or infection
  • Radiotherapy
31
Q

Growth hormone resistance is also known as______.

A

Laron dwarfism

32
Q

How does GH resistance occur?

A
  • GH binding protein mutations which carry through the blood
  • GH receptor mutations
33
Q

What is somatropin?

A
  • 7 preparations of somatropin available in UK
  • Produced by recombinant DNA technology
  • Sequence identical to that of human GH protein
34
Q

What is the name of the structure that magnocellular neurons in the hypothalamus pass through?

A

Infundibulum (and end in the posterior pituitary gland)

35
Q

What two hormones do magnocellular neurones sythensize and secrete?

A

Oxytocin and vasopressin (ADH)

The hormones are released at the axon terminals, where they diffuse into the capillary network of the posterior lobe

ADH and oxytocin do NOT go through the portal system

36
Q

Functions of oxytocin:

A
  1. Stimulation of milk ejection (not secretion)
  2. Stimulation of uterine smooth muscle contraction at birth
  3. Establishment of maternal behaviour
37
Q

Describe child birth as a positive feedback regulation:

A
  1. Pressure on cervix activates sensory nerves
    2) Oxytocin is released in waves from the hypothalamus
    3) Receptors in the uterus response and the uterus contracts

Once baby removed from cervix, pressure removed therefore reflex ark stops.

38
Q

Synthetic oxytocin used in labour:

A
  • Can be used if labour isn’t progressing to speed up contractions
  • Problems – if contractions occur too quickly and strong, blood supply can be reduced to the baby. Has to be carefully monitored.
  • Can starve the baby’s brains of oxygen
39
Q

Functions of vasopressin (ADH)

A
  • Keeps us hydrated
  • Binds to receptors on cells in the collecting ducts of the kidney
  • Synthesis and insertion of aquaporins into kidney tubules.
  • Promotes reabsorption of water back into the circulation
  • In the absence of vasopressin, the collecting ducts are virtually impermeable to water, which therefore flows out as urine
40
Q

What is diabetes insipidus?

A

Excessive urine production - as much as 16 litres of urine per day!

41
Q

Two main causes of diabetes insipidus?

A

1) Hypothalamic (“central”) diabetes insipidus
• Deficiency in vasopressin secretion
• Caused by: head trauma, infections or tumors involving the hypothalamus
• Treat using exogenous vasopressin as it is simply due to a lack of ADH

2) Nephrogenic diabetes insipidus
- Kidney is insensitive to vasopressin
- Caused by: renal disease, mutations in the vasopressin receptor gene or in the gene encoding aquaporin-2 (effector for vasopressin)
- Treat by increasing water consumption – no drug treatment

42
Q

Length of the pineal gland?

A

6mm

43
Q

Where is the pineal gland located?

A

• Located in the epithalamus, between the 2 hemispheres, in centre of brain

44
Q

Name of the cells that secrete the hormone melatonin?

A

Pinealocytes

45
Q

What rhythm does melatonin help regulate?

A

Circadian rhythm.

Melatonin has been shown to be effective in treating seasonal affective disorder (SAD) and insomnia caused by poor quality sleep.

The Patient Y3 semester 1 (17 decks)

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