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MP > L24 > Flashcards

L24 Flashcards

1
Q

explain the hypothalamic pituitary axis

A
  • The hypothalamus + the pituitary gland work together to control other endocrine glands
    • Connected by the infundibulum
    • The anterior lobe of the pituitary glands make up 75% of the weight of the pituitary glands + secrete 7 hormones (from 5 different cell types)
    • The hypothalamus secretes releasing + inhibiting hormones that control the release of hormones by the anterior pituitary gland
    • Reach the pituitary gland via the hypophyseal portal system
      The posterior lobe of the pituitary gland made of anural tissues + releases 2 hormones made by the hypothalamus
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2
Q

label the pituitary lobes of the brain

A

REFER TO ONENOTE

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3
Q

//explain the hypothalamus + the anterior pituitary

A
  • Hypothalamus releases hormone 1, acts at
    • Anterior pituitary to affect release of hormone 2, acts at
    • Endocrine gland to affect release of hormone 3
    • Acts at target tissues
      Neg. Feedback loops control the secretion of 3 hormones
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4
Q

what are the hormones secreted by the anterior pituitary

A
  • TSH (throud stimulating hormone) for Thyroid
    • Prolactin for Mammmary gland
      Growth hormones for Bone, muscle, and adipose tissues
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5
Q

//explain the thyroid hormone loop

A

Hypothalamus releases TRH, to anterior pituitary, releases TSH (which can go back to hypothalamus in short loop), from TSH can go to target endocrine gland, release thyroid hormones T3 + T4 (can go back to anterior pituitary and hypothalamus in long loop), goes to target cell

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6
Q

explain the thyroid gland

A
  • Is a butterfly shaped gland, located inferior to the larynx + anterior to the trachea
    • Has right + left lateral lobes connected by an isthmus
    • Follicular cells stimulated by TSH to produce T4, T3 (difference is no. Of iodines attached) - known as thyroid hormones
      Parafollicular cells (C cells) produce the hormone calcitonin, helps regulate calcium homeostasis
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7
Q

explain the production of thyroid hormones

A
  • Thyroid hormones synthesised by attaching iodine atoms to the amino acid tyrosine
    • Binding 1 iodine atom to TGB (thyroid binding globulin) produces T1, binding of another idonine atom produces T2
    • 2 T2 moleucles couple to form T4, or 1 T1 and 1 T2 couple to form T3
      T3/T4 are transported in blood bound to TBG
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8
Q

explain the effects of the thyroid hormone

A
  • Increases basal metabolic rate (BMR)
    • Help maintain normal body temp.
    • Stimulates protein synthesis
    • Increases the use of glucose + fatty acids for ATP production
    • Upregulates beta adrenergic beta receptors
      Works with GH and insulin to accelerate body growth
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9
Q

//explain the regulation of thyroid hormone

A
  • Hypothalamus secretes TRH to stimulate
    • Anterior pituitary to release TSH, this stimulates the synthesis + release of thyroid hormones from thyroid
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10
Q

explain hypothyroidism

A
  • deficiency of thyroid hormone
    Gain weight + cold
    • In children- cretinism
    • Adults- myxoedema
    • Hashimotos thyroiditis
      ○ Autoimmune disease
      Occurs when body make antibodies that attack the cells in your thyroid
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11
Q

explain hypothyroidism in infants

A
  • Leads to growth + mental retardation
    • Treated with T3/T4
    • Low iodine intake leads to reduced T4 + T3 production, thus hypothyroidism
      That’s why we have iodised salts (so people get enough iodine)
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12
Q

explain hypothyroidism in adults

A
  • Produces myxoedema (long standing hypothyroidism)
    • Fatigued, coldness, weight gain, slow reflexes, weak pulse
    • Decreased cardiac output, respiration, and anaemia
    • Reduced BMR
    • Can lead to coma
      Treatment is thyroid hormone replacement
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13
Q

explain hyperthyroidism

A
  • Excess thyroid hormone = thyrotoxicosis
    Loss weight + hot
    • Most common cause is Graves disease
      ○ Autoimmunity against TSH receptors
      ○ Antibodies mimic effect of TSH
    • Leads to irritability, weight loss, fever, fast/irregular heart rate, heart failure in elderly, eye disease, skin lesions
      In children lead to behavioural disorders
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14
Q

explain graves disease

A
  • Most common hyperthyroidism (1% of population)
    • Autoimmune disease
    • Females 3-5x more likely
      Due to an antibody that icnreases growth + function of thyroid
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15
Q

explain goiters

A
  • Enlarged thyroid
    • Due to either hyperthyroidism or hypothyroidism
      Depends on the cause and the hypothalamo-pituitary-thyroid feedback loops
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16
Q

//explain hypothyroidism due to low iodine

A
  • Decreased iodine in diet
    ○ Decreases T3 + T4
    ○ Affects hypothalamus
    ○ Increases TRH release
    ○ Goes to anterior pituitary
    ○ Increases TSH release
    ○ Goes to target cell, enlarges thyroid gland
    ○ No iodine left
    Decreases T3 + T4, no neg. Feedback loop
17
Q

//explain hyperthyroidism due to Graves’ disease

A
  • Starts from hypothalamus, decreases TRH, no stimulus in anterior pituitary, so no TSH released
    Thyroid stimulating immunoglobulins release, enlarge thyroid gland, increases T3 + T4- strong neg. Feedback loop
18
Q

explain growth hormone

A
  • From the anterior pituitary
    • Human growth hormone (hGH) is the most plentiful anterior pituitary hormone
    • Released in bursts every few hours
      Controlled by 2 hypothalamic hormones- GHRH + GHIH
19
Q

explain GHRH

A

§ Release stimulated by low blood glucose (hypoglycaemia), anterior pituitary releases GHRH, GHRH stimulates secretion of hGH by somatotrophs
§ hGH and IGFs speed up breakdown of liver glycogen into glucose, which enters the blood more rapidly
§ Blood glucose levels rises to normal (about 90mg/100ml)
If blood glucose continues to increase, hyperglycaemia inhibits release of GHRH

20
Q

explain GHIH

A

§ Release stimulated by high blood glucose (hyperglycaemia), anterior pituitary releases GHIH, GHIH stimulates secretion of hGH by somatotrophs
§ hGH and IGFs slow down breakdown of liver glycogen into glucose, which enters the blood more slowly
§ Blood glucose levels fall to normal (about 90mg/100ml)
§ If blood glucose continues to decrease, hypoglycaemia inhibits release of GHIH

21
Q

explain the actions of growth hormones

A
  • Growth hormone has a effect on liver + other tissues
    • Causes them to release insulin like growth factors (IGF)
    • Does indirect growth promoting actions, has skeletal effects and extra skeletal effects
    • Skeletal effects- increased cartilage formation and skeletal growth
      Extra skeletal effects- increased protein synthesis + cell growth + proliferation
22
Q

explain congenital vs acquired disorders from GH defiencies in children

A
  • Congenital
    ○ Decreased birth length
    ○ Decreased growth rate
    ○ Delays in puberty
    • Acquired
      Problems start on acquisition
23
Q

explain gigantism

A

§ Can be either congenital or acquired
§ Due to excessive GH secretion before adolescence
§ Due to tumours
§ Person grows in proportion initially
Usually die young (pituitary glands no longer work)

24
Q

explain acromegaly

A

§ Mostly acquired
§ If hypersecretion of GH occurs post puberty
§ Bone growth in hands, feet, and face
§ All organ sizes increase- hypertension
Needs surgical removal of tumour

MP (29 decks)

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