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Medicine > Endocrine > Flashcards

Endocrine Flashcards

1
Q

What general system controls cortisol release

A

The HPA axis (hypothalamic pituitary adrenal axis)

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2
Q

What is cortisol

A

A glucocorticoid produced by the zona fasciculata of the adrenal gland

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3
Q

What are the initial stimuli for the HPA axis cortisol release

A

Stress, infection, blood loss, diurnal rhythm (sleep wake cycle)

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4
Q

What is the pathway of cortisol release

A

1) Stimulus
2) Corticotropic releasing hormone (CRH) from hypothalamus
3) CRH binds to corticotrope cells in anterior pituitary
4) ACTH is releases from anterior pituitary
5) ACTH travels in blood and binds to MC2r receptor in adrenal cortex
6) Cortisol released from zona fasciculata
7) Cortisol acts on tissues in the body via nuclear receptor

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5
Q

What are the byproducts of ACTH formation

A

melanocyte stimulating hormone, endorphins, enkephalins

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6
Q

What does cortisol do

A
  • Gluconeogenesis
  • Lipolysis
  • Increase of proteins –> amino acids
  • Immunosuppression + anti-inflammation
  • Regulates behaviour, mood, cognition
  • Increase in appetite
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7
Q

Can cortisol pass through the phospholipid bilayer

A

Yes. It binds to a glucocorticoid receptor in the cytoplasm. The glucocorticoid-cortisol complex can pass into the nucleus

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8
Q

What are nuclear receptors

A

Receptors that are found either in the cytoplasm or the nucleus of a cell

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9
Q

What are the 2 endogenous glucocorticoids

A

Cortisol and corticosterone

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10
Q

What is the negative feedback of the HPA azis

A
  • ACTH and cortisol inhibit CRH release from hypothalamus
  • Cortisol reduces the sensitivity of corticotropin cells in a pituitary, so release less ACTH
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11
Q

How are glucocorticoids transported in the blood

A
  • 90% bound to corticosteroid binding globulin (CBG)
  • 5% bound to albumin
  • 5% free
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12
Q

What does the zona glomerulus secrete

A

Mineralcorticoids eg aldosterone

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13
Q

What does the zona fasciculata secrete

A

Glucocorticoids - cortisone + corticosteroid

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14
Q

What does the zona reticularis secrete

A

Androgen precursors (converted into testosterone or oestrogen in the gonads)

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15
Q

What are the layers of the adrenal gland outside –> in

A
  • Capsule
  • Zona glomerulus
  • Zona fasciculata
  • Zona reticularis
  • Adrenal medulla

–> Growing means finding great raves aswell

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16
Q

What can a tumour of the pituitary gland cause

A

Bitemporal hemianopoiea –> compresses optic chiasm crossing fibres, causes temportal loss of vision

17
Q

What is the thyroid gland composed of

A

Thyroid follicular cells surrounding colloid (fluid)

18
Q

What system controls thyroid hormone release

A

Hypothalamic-pituitary-thyroid axis

19
Q

What are the thyroid hormones

A

T4 = Thyroxine
T3 = triiodothyronine
(calcitonin but this isn’t really counted)

20
Q

What is the HPT axis

A

1) Thyrotropin releasing hormone (TRH) from hypothalamus
2) TRH causes Thyroid stimulating hormone (TSH) to be released from thyrotrophs in anterior pituitary
3) TSH stimulates T3/T4 release from the thyroid gland

21
Q

How is thyroxine produced

A

By thyroid peroxidase in thyroid gland adding iodide to tyrosine

22
Q

How + where is T4 converted to T3

A

Via the deiodination of T4 in the liver, kidney, muscles

23
Q

What is the negative feedback of the HPT axis

A

T3 desensitises anterior pituitary and inhibits TSH secretion from anterior pituitary

24
Q

How are T3/T4 transported in the blood

A

They are hydrophobic so 99% are transported bound to proteins, mostly thyroid-binding-globulin

25
Q

Where is the parathyroid gland

A

4 bits of tissue on the back of the thyroid gland

26
Q

Primary hypo/erthyroidism

A

The pathology is in the thyroid gland

27
Q

Secondary hypo/erthyroidism

A

The pathology is in the hypothalamus/anterior pituitary causing changes to TSH levels

28
Q

What cells secrete calcitonin

A

parafollicular cells (C CELLS)

29
Q

What are the divisions of the pituitary gland

A

Anterior and posterior

30
Q

What does the posterior pituitary secrete

A

Oxytocin and ADH (only secrete, produced by hypothalamus)

Medicine (15 decks)

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