Hypothalmic and Pitiutary Hormones

Question 1

where is the hypothalmus located?

Answer 1

located below the thalamus, just above brain stem

Question 2

what is the role of the hypothalmus?

Answer 2

important for control of basic fucntions such as hunger, thirst, sleep.
it senses the internal and external environment.

Question 3

where is the pituitary gland?

Answer 3

sits in the small bone cavity, below the hypothalumus.

it is the size of a pea and weight around 0.5g

Question 4

what is the role of the pituitary gland?

Answer 4

Connects to hypothalamus via the infundibulum or pituitary stalk. There are different ways in which they will communicate

Question 5

what are the parvicellular neurons?

Answer 5

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

Question 6

what are the magnocellular neurons?

Answer 6

have long axons which extend down into the posterior pituitary lobe (direct neuro-endocrine link). It the neurones that secrete the hormones and carry the neurones down the nerve axons to the terminals which are found in the posterior pituitary.

Question 7

The anterior pituitary does NOT have a direct nervous connection with the hypothalamus?

Answer 7

TRUE

Question 8

what secretes hormones from hypothalmus which reach target sites?

Answer 8

hypothalamic-pituitary portal system

Question 9

what are all the hormones produced by hypothalmus or pituitary gland?

Answer 9

peptides or small proteins (bar dopamine)

Question 10

what is prolactin?

Answer 10

hypothetical hormone

Question 11

where are hypothalmic regulatory hormones secreted directly into?

Answer 11

portal system = hypothalamic-pituitary portal vei

Question 12

what are the tropic hormones?

Answer 12

FLAT

• follicle stimulating hormone (FSH)
• luteinising hormone (LH)
• adrenocorticotropic hormone (ACTH)
• thyroid stimulating hormone (TSH)

Question 13

what are the non-tropic hormones?

Answer 13

• prolactin (PRL)

- growth hormone (GH)

Question 14

what is the functions of FSH and LH (gonadotropin)?

Answer 14

• 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

Question 15

what is the function of ACTH (corticotropin)?

Answer 15

• Synthesised, stored & secreted from
corticotropes
it also regualtes to levels of cortisol within the body

Question 16

what happens when there is a decreased temperature?

Answer 16

• change in temp
• hypothalmus detects and release thyrotroping releasing hormones
• this is detected by anterior pituiarty which secretes thryoid stimulating hormones
• tropic then reaches endorcrine gland release thryoid hormoes and increases metabolsim and therefore increased heat production

Question 17

what is a short loop feedback?

Answer 17

it means it jumps up one endocrine axis

Question 18

what is a long loop feedback?

Answer 18

jumps up two levels in an endocrine axis

Question 19

whats an ultra short loop?

Answer 19

inhibits secretion of its own hormone

Question 20

what is the function of the anterior pituitary hormone?

Answer 20

Non-tropic hormones Prolactin and Growth Hormone (GH) (PiG) act directly on other tissues and do not work on another endocrine system

Question 21

what is prolactin?

Answer 21

• 198-amino acid, single-chain polypeptide
• Synthesized, stored, & secreted by lactotropes
• Roles and functions complex
• includes effects on breast tissue for lactation
• Dysregulation causes multiple problems which affect many different body systems
• Most common pituitary tumour is prolactinoma tumour of lactotrope cells
• Treated using dopamine receptor agonists
• e.g. bromocriptine, cabergoline

Question 22

what is growth hormone?

Answer 22

• 191-amino acid, single-chain polypeptide
• Synthesized, stored, & secreted by somatotropes in the anterior pituitary
• Stimulates growth, cell reproduction and regeneration of specific cells
- Hypersecretion of growth hormone causes gigantism in children….Before the long bones have fused you have lots of growth in these
- and acromegaly in adults this is after long bones have fused.
o enlargement of the head, hands, feet, lower jaw, tongue and lips
o excessive sweating, headaches and visual field loss, due to pressure on optic nerve from the tumour right next to the pituitary gland.

Question 23

what is the treatment for acromegaly?

Answer 23

• 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
• If there is a tumour it can be removed with surgery but drug treatment is always used for as it is hard to get access to the pituitary gland.

Question 24

when would you have insufficinet hormone production of growth hormone?

Answer 24

• Hypothalamic or pituitary tumor not a tumor which is secreting too much but it is pressing too much on the stalk and prevents the signals getting from hypothalamus to the pituitary so can therefore reduce secretion of the hormone
• (craniopharyngioma most common)
• Mutation of GH genes
• Head injury or infection
• Radiotherapy

Question 25

what is GH resistance?

Answer 25

genetic • GH binding protein mutations which carry the hormone in the blood • GH receptor mutations

Question 26

how many prepartions of somatropin are there

Answer 26

seven

Question 27

what is a drug for severe hypopituirism?

Answer 27

protirelin

Question 28

what is gonadorelin?

Answer 28

induces FSH and LH

Question 29

what is the function of the posterior pituitary?

Answer 29

* Magnocellular neurons (produce hormones) in the hypothalamus pass through the infundibulum and end in the posterior pituitary gland * These neurons synthesize and secrete oxytocin and vasopressin (ADH). Quite rare to have both secreted from one. * The hormones are released at the axon terminals, where they diffuse into the capillary network of the posterior lobe and then will be transported to rest of the body * ADH and oxytocin do NOT go thro’ the portal system moving directly to the capillaries which supply rest of the body

Question 30

what are the functions of oxytocin?

Answer 30

1. Stimulation of milk ejection – not milk production! 2. Stimulation of uterine smooth muscle contraction at birth 3. Establishment of maternal behaviou

Question 31

how does oxytocin work?

Answer 31

During child birth positive feedback regulation. Pressure on cervix cause a reflex arc up to the hypothalamus and causes a release of oxytocin, this will be transported in blood and picked up in uterus and this causes the uterus to contract, this causes a cycle. Once baby is out of uterus the pressure will have gone and this would then mean there would no longer be a reflex arc so no more oxytocin being released.

Question 32

when would you use sythentic oxytocin?

Answer 32

for induction of labour, speeds up contractions but this can come with problems.

Question 33

what are the problems of inducing labour with syntheitc oxytocin?

Answer 33

If the contractions are too quickly and too strongly – this will cause a reduce blood supply to the baby and therefore this means there is less oxygen getting to the baby and it can cause cerebral palsy. You therefore need to monitor very closely when it is given.

Question 34

what is the function of vasopressin (ADH)?

Answer 34

Binds to receptors on cells in the collecting ducts of the kidney • When the hormone binds it causes Synthesis and insertion of aquaporins into kidney tubules • Promotes reabsorption of water back into the circulation via aquaporin 2 channel

Question 35

what happens is the absence of vasopressin?

Answer 35

the collecting ducts are virtually impermeable to water, which therefore flows out as urine – reducing water content of the body and the blood. Important for water balance.

Question 36

what is a symptom of diabetes insipidus?

Answer 36

excessive urine production - as much as 16 litres a day

Question 37

what causes hypothalamic diabetes insipidus?

Answer 37

* Deficiency in vasopressin secretion * Caused by: head trauma, infections or tumors involving the hypothalamus * Treat using exogenous vasopressin simply due to a lack of vasopression so can be given as an injection

Question 38

what causes nephrogenic diabetes insipidus?

Answer 38

* Kidney is insensitive to vasopressin * Caused by: renal disease, mutations in the vasopressin receptor gene or in the gene encoding aquaporin-2, effector of vasopressin * Treat by increasing water consumption, no drug treatment as there isn’t a problem with the production of vasopressin. Not usually life threatening aslong as they can get the water.

Question 39

where is the pineal gland located?

Answer 39

Located in the epithalamus, between the 2 hemispheres, in centre of brain. Nothing to do with the pituitary- separate gland. secrete melatonin

Question 40

what is melatonin needed for?

Answer 40

* Melatonin helps regulate the circadian rhythm governs a lot of physiology and controls what happens in day and night as these do differ * Production of melatonin by the pineal gland is inhibited by light to the retina and permitted by darkness