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LC 3 > LC 3.4 Ageing and the Endocrine System > Flashcards

LC 3.4 Ageing and the Endocrine System Flashcards

1
Q

By what possible mechanisms can ageing affect the endocrine system?

A

Reduced synthesis or turnover of hormones

Defective binding

Impaired post-receptor activation

Increased prevalence of endocrine autoimmune disease

Increased prevalence of adenomas or malignancies

Menopause/andropause

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2
Q

What causes decreased vitality in the elderly?

A

endocrine disease

metabolism and nutritional factors

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3
Q

What generally happens to circulating hormone levels with age and why?

A

Remains the same

Atrophy and fibrosis of endocrine glands causes decreased secretion

However, there is decreased breakdown and clearance due to decreased kidney and liver sizes

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4
Q

What changes occur in target tissues with age?

A

Less responsiveness to hormones

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5
Q

What changes occur in the HPT (hypothalamic pituitary thyroid) axis with age?

A

A progressive loss of sensitivity to feedback control

Blunted TSH response to TRH

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6
Q

Which key hormones are affected by ageing?

A

T3 triiodothyronine (active version)

PTH (increases)

Free testosterone

Insulin

Vasopressin

Noradrenaline

GH

DHEA dihydroepiandosterone

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7
Q

Which form of thyroid hormone is measured in blood tests?

A

T4

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8
Q

Which neurones are found in the hypothalamus which are involved in the HPA axis for sexual reproduction?

A

GnRH neurones - secrete GnRh

KNDy neurones - negative feedback control

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9
Q

Why does the sexual HPA axis shut down if you are too skinny?

A

Adipose tissue produces leptin which up-regulates the axis through KNDy neurones.

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10
Q

What effect does stress have on the sexual HPA axis?

A

Inhibits hypothalamus neurones, to inhibit the axis

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11
Q

What causes most changes to the HPT axis?

What changes are brought about by this?

A

Illness

Effects of medications:
NSAIDs
Radiocontrast agents
Iodine-containing compounds

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12
Q

What does GnRH stimulate the secretion of?

A

LH and FSH

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13
Q

What effects does illness have on the HPT axis?

A

decreased T3

if severe, decreases T4

Blunted response of TSH to TRH

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14
Q

The reduction in production in thyroid hormone due to ingestion of iodine containing compounds (such as radiocontrast agents)?

A

Wolff-Chaikoff effect

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15
Q

In healthy elderly, what are the changes in T3, T4 and TSH production and ranges

A

T3 production decreases 30%, range same

T4 production decreases 25%, range same

TSH production and range increases

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16
Q

What is the diagnosis for hypothyroisim?

A

Low free T4 and high TSH

17
Q

What are the symptoms of hypothyroidism?

A 
Fatigue and sluggishness
Dry skin
Slow pulse
Croaking speech
Frank dementia
18
Q

What causes primary hypothyroidism? (lightbulb is broken, not turned off [secondary])

A

Autoimmune thyroiditis

Thyroidectomy

Radiation

Lithium

Impaired intake of L-T4 medication

19
Q

Why does lithium cause primary hypothyroidism?

A

It inhibits T4 and T3 release from the gland

20
Q

What is HYPERthyroidism induced by iodine such as those found in radiocontrast agents called?

A

Jod-Basedow phenomenon

Doesn’t occur people with normal thyroid glands

21
Q

What can cause impaired intake of L-T4 medication?

A

Iron supplements

Bile acid sequestrants

22
Q

What causes secondary hypothyroidism?

A

Posterior pituitary surgery

23
Q

Why is TSH level useless for diagnosis and monitoring of secondary hypothyroidism?

A

Because there is low TSH level

24
Q

What is overt hypothyroidism?

A

Increased T4

decreased TSH

25
Q

What is subclinical hyperthyroidism and which gender is it more common in?

A

High-normal T3 & T4

Low TSH

26
Q

What are the causes of hyperthyroidism?

A

Toxic multinodular goiter

Grave’s disease

27
Q

What does the hypothalamus release with relation to the Growth Hormone and IGF-1 axis?

A

GHRH

Somatostatin (GHInhibitingH)

28
Q

What does GH do? (i.e. act on, etc.)

A

Stimulates hepatic and local production of IGF-1

GH and IGF-1 work synergistically

29
Q

What does GH cause?

A

Linear growth in childhood

Metabolic changes:
Fat breakdown
Early insulin resistance

30
Q

What is the effect of age on GH production? What are the mechanisms for this?

A

GH production declines by 14% with every decade of ageing

CAUSED BY:
   • Reduced pituitary function
   • Increased hypothalamus somatostatin
   • Decreased GHRH activity
   • Menopause and andropause (because E2 stimulates GH)
31
Q

What does the change in GH with age lead to?

A
  • Increased body fat
    • Decreased muscle mass
    • Decreased bone mass
    • Fat redistributed from subcutaneous to central visceral sites
    • Decreased IGF-1
32
Q

What does the change in IGF-1 (due to the change in GH)with age lead to?

A

• Increased apoptosis (because IGF-1 decreases apoptosis)

33
Q

How can the effects of GH change with age be reversed?

A

Give GH to elderly

Exercise (increases GH levels in elderly)

34
Q

How does calorie restriction retard physiological ageing?

A

Food restriction reduces pituitary hormone secretion

GH accelerates ageing and shortens life

35
Q

Describe the importance of a correct GH balance

A

GH accelerates ageing if too high, but causes negative morphological changes if too low.

A balance is needed for optimal life expectancy

36
Q

What is the age effect on sex steroids and corticosteroids? What can exacerbate these changes?

A

Adrenal androgens decline

Aldosterone declines

Cortisol during evenings and at night increase with age (morning is normal)

Exacerbated by dementia

37
Q

What causes the increase in cortisol with age?

A

Impaired HPA steroid feedback

38
Q

What can increased cortisol with age cause and why?

A

Type 2 diabetes mellitus and CVD due to anti-insulin effects (catabolic)

Damage to cell regeneration machinery due to:
• increased free radicals
• increased arachidonic acid
• increased intracellular calcium

LC 3 (12 decks)

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