endocrinology of ageing

Question 1

hormones- amino acid derivatives

Answer 1

small molecules structurally related to individual amino acids
derivatives of tyrosine - thyroid hormones (secreted by thyroid gland) and catecholamines- secreted by hypothalamus
derivatives of tryptophan- melatonin - secreted by pineal gland

Question 2

peptide hormones

Answer 2

chains of amino acids
glycoproteins
short polypeptides and small proteins

Question 3

lipid derivatives

Answer 3

carbon rings + side chains built from fatty acids or cholesterol
eicosanoids- lipid derivatives of arachidonic acid
steroid hormones- structurally similar to cholesterol

Question 4

intracellular receptors

Answer 4

amino acid derivatives
mitochondrial receptors increase ATP production, nuclear receptor binding activates specific genes

Question 5

cell membrane receptor

Answer 5

amino acid and peptide hormones
binding triggers signalling cascade involving G priteins, cAMP, cGMP and kinases that alter enzyme activity

Question 6

intraceullular recpetors

Answer 6

lipid derivatives
binding of hormone receptor complex to dna activates specific gene

Question 7

hormones + ageing

Answer 7

factors affecting hormone levels in older people
- changes in kidney and liver lead to reduced metabolic clearance (changes how quickly hormones are broken down)
- steroid hormones bound to carrier proteins/albumin- decrease in carrier protein synthesis will reduce serum concentrations are steroids are not water soluble
- increased prevalence of conditions that affect endocine system
- negative feedback regulation may complicate interpretation of changes- some glands may be mroe active to make up for a lack of a hormone
- sleep disturbance may affect prod of hormones with circadian rhythm
- general anatomy can affect production of some hormones

Question 8

effects of GH

Answer 8

metabolism
-protein synthesis, fat breakdown and glucose production
- high IGF1 associated with increased risk of cancer
- low IGF1 associated with increased risk diabtes, CHD and ostoeporosis

Question 9

GH + IGF1 and ageing

Answer 9

reduced hypothalamic secreted of GHRH (growth hormone releasing hormone)
no decrease in piruitary somatotroph cells
substantial decline in GH and IGF1 production- both basal and in response to stimulation

Question 10

pancraeas

Answer 10

pancreatic islets- involved in production of insulin
when blood glucose levels increase, is detected by beta cells, produce insulin and lower glucose by: increasing rate of glucose use, increasing transport of glucose into cells
alpha cells produce glucagon when glucose levels are low
glycation- when glucose levels are too high

Question 11

glucose uptake

Answer 11

facilitated by insulin
glut4 transported to surface, allowing more glucose to be taken up by the cell

Question 12

impaired insulin secretion

Answer 12

consequences
- hyperglycemia
- reduce glycogen production
- reduced AA absorption and protein synthesis
- reduced glut4 translocation to membrane
- reduced cellular uptake of glucose

Question 13

glucose metab + ageing

Answer 13

reduced sensitivity of B cells
less effective insulin
decreased rate of response
less insulin production
less insulin response to glucose tolerance test

Question 14

insulin resistance

Answer 14

target organs become less sensitive to insulin
less glucose removed for given insulin level
higher blood glucose
intitially compensated by increased insulin secretion
may be related to changes in glut 4 transporter

may be related to inactivity and

Question 15

type 2 diabetes

Answer 15

affects 1 in 5 older people
impaired insulin secretion and or action
elevated blood glucose levels- increased glycation reactions
microvascular damage contrubutes tp pathology - sensory nerves, retinas, kidneys
risk factors- obesity (visceral fat), age and inactivity
responds to exercise and dietary management

Question 16

why regular exercise can help

Answer 16

increases glut4 content
increases independent glucose uptake by muscle
higher insulin sensitivity
lower blood glucose
lower insulin

Question 17

effect of thyroid on peripheral

Answer 17

elevated o2 and energy consumption
increased HR and force of contraction
increased sensitivity to sympathetic stimulation
stimulates RBC formation
accelerates bone turnover
most actions mediated by T3 (more biologivcally active) although T4 is present in larger quantity

thyroxine - t4

Question 18

thyroid/thyroid hormone +ageing

Answer 18

changing in healthy adults vary
- decreased size of thyroid follicles, fibrosis
- intrafollicular colloid declines but higher prevalence of nodules
- slight decrease in t3 levels, slower clearance
- little change in t4 levels
- reduced peripheral t4 to t3 conversion

Question 19

hypothyroidism

Answer 19

ageing increases prevalence
- affects 5-10% of older women
- low t4 + elevated tsh
- thought to be result of autoimmune disease
- symptoms - sluggishness, weight gain, intolerance to cold, low HR

treating- increases T4 which would lead to increased t3, decreased tsh, increased metabolic rate

Question 20

parathyroid glands/hormone

Answer 20

PTH levels increase with age
more marked increase associated with- inadequate dietary calcium, oestrogen deficiency, inadequate vit
D
consequence of hyperparathyroidism- bone loss

Question 21

adrenal medulla

Answer 21

hormones- adrenalin and noradrenalin
produce vasoconstriction, increased HR, mobilisation of glucose and fatty acids in response to sympathetic stimulation from hypothalamus

changes with ageing
- basal concentrations of adrenaline and noradrenaline increase with age
- response to stimulation decreased with age

Question 22

adrenal gland

Answer 22

medulla- catecholamines - fight or flight response, increased blood glucose and HR

zona reticularsis- androgens (sex steroids)

zone fasciculate- glucocorticoids eg cortisol, promote glucose synthesis, fat and protein catabolism, anti infllammatory efects

zona glomerulosa- mineralcroticoids eg aldosterone, affect electrolyte compisition

Question 23

adrenal cortex- DHEA

Answer 23

dehydroepiandrosterone
- weak androgen
- DHEA levels substantially lower with age
- declines associated with reduced muscle and bone mass
- little effect of supplementation

Question 24

adrenal cortex- glucocorticoids

Answer 24

cortisol
- stress response - anti inflammatory and catabolic effects
- shows substantial circadian variation
- with ageing- increases in basal levels but circadian variation reduces
- increased cortisol production in skin
- cortisol excess may contribute to glucose intolerance, bone loss, memory loss, fat redistribution

Question 25

adrenal cortex- mineralcorticoids

Answer 25

aldosterone works with angiotensin , ADH
retention of Na+ and water, maintainence of blood volume
kidney becomes less responsive with ageing
reduced ability to retain water and sodium with age