Stress hormones

18 important questions on Stress hormones

Describe the growth hormone axis.

Growth hormone releasing hormone (GHRH) is released in the  hypothalamus. This stimulates the anterior pituitary to release growth hormone (GH). The liver makes somatomedins, which have a negative feedback to the hypothalamus.

What are the effects of growth hormone?

  • Inhibition of glucose uptake and utilization
  • Increased AA uptake and protein synthesis
  • FA mobilization (in fat cells)
    • FA uptake and utilization (in muscle)
    • Protein synthesis (in muscle)
    • KB synthesis (in liver)
  • Glucose and somatomedins release (in liver) (negative feedback)

Why does growth hormone increase under stress and fasting conditions?

GH has this effect of mobilizing fat reserves and for that reason GH also increases under stress and fasting conditions.
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What is a circadian rhythm?

That the level of a certain hormone have a peak at a certain moment during the day.

What is the circadian rhythm of GH?

GH is highest at night

What are the effects of glucocorticoids?

  • In fat cells: breakdown of lipids and release of FA (mobilize FA as energy source)
  • In the liver: stimulates gluconeogenesis, release of glucose, and deamination of AA
  • In the muscle: proteins are broken down (net loss of AA)

What is the circadian rhythm of the HPA-axis?

It is high during the day (your body is most in need of food during the day).

There are different types of stress responses. What are these and what is the difference?

Specific stress response: activation of the sympathetic nervous system
  • Release of adrenaline: more alertness
Generalized stress response: activation of HPA-axis

What is the exhaustion phase?

The exhaustion phase means that the stress situation persists for a really long time. This can be lethal.

What is Addison's disease?

Hypocortisolism, a too low level of cortisol (glucocorticoids). There are two types:
  • Primary: cortisol production not sufficient
  • Secondary: ACTH production not sufficient
Energy reserves cannot be mobilized in any condition.

What is Cushing's disease?

Hypercortisolism, a too high level of cortisol (glucocorticoids) in your blood. This leads to an excessive breakdown of protein and lipid reserves. It leads to upper body obesity.

What is upper body obesity?

It means that the protein and lipid reserves in your arms and legs are broken down. However, you don't need all this fat and it accumulates in your neck.

What is the function of the thyroid hormones?

Increase oxygen consumption to produce heat.

What is the circadian rhythm of the HPT-axis?

It is high during the night because then you are more prone to a low body temperature since you're laying still and not moving.

How is thyroid hormone synthesized?

You need to synthesize a protein called thyroid globulin (TGB). TGB contains tyrosine and it is used to transport tyrosine to the cell surface and then the empty space (lumen). In the lumen the iodine molecules are being coupled to the tyrosine that is in the TGB. Then the TGB (with iodinated tyrosine) is taken up into the cell agin. Here the TGB is being degraded and then you're left with iodinated tyrosine, which are the thyroid hormones.

How are the thyroid hormones transported?

Thyroxine-binding globuline (TBG)

How can you treat myxedema?

Thyroid hormone: levothyroxine

How can you treat Graves' disease?

Radioactive iodine treatment. The radioactive iodine radiates the thyroid gland and you hope to go back to the normal situation. This is hard so many patients have their thyroid gland removed by surgery.

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