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Endocrinology Flashcards

1
Q

What is endocrinology?

A

Study of endocrine glands and their secretions

Hormones help maintain normal homeostasis

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2
Q

What do hormones do?

A

Tell cells what to do
Results in the production of a protein that has some effect on the body
Most have another hormone that regulates its’ secretion

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3
Q

What are the elements of the enodcrine system?

A 
Pituitary
Pineal
Thyroid
Thymus
Adrenal
Pancreas
Ovaries/Testes
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4
Q

What is the pituitary gland?

A

The ‘master gland’- has extensive influence on other organs
Linked to the hypothalamus; stimulates and inhibits pituitary hormones
Responsible for making hormones to stimulate organs to act

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5
Q

What are the 4 stages of growth?

A 
Foetal 
Infancy
Childhood
(GH/GF axis 4-8cm/yr)
Puberty/Adolescence 
(sex steroids and GH 8-10cm/yr)
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6
Q

Describe growth in utero

A

Growth dependent on the mother’s genetics. Also the mother’s health. Placental nutrition and function
Most rapid period of growth
Peaks at 10cm per month around 13-18 weeks gestation

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7
Q

What are the maternal factors of growth?

A

Mother’s health will impact the baby; i.e. smoking and alcohol
Chronic disease, i.e. hypertension

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8
Q

Describe growth in infancy

A

Linear growth is initially rapid; 25cm in the first year of life
Continuation of the fetal growth pattern
Growth rate declines
Most important influencing factor is nutrition

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9
Q

Describe growth in childhood

A 
Period of relatively steady growth
Body proportions more adult like
Children are slender, leggy and agile
Little difference in the growth rates between girls and boys
Growth rate 4-7cm/year
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10
Q

What are the impacts of the endocrine system on growth?

A

Nutrition becomes less important
Hormonal influences;
-principle regulating mechanisms for linear growth
-growth hormone
-insulin-like growth factor (IGF-1)
-thyroid hormone;
hypothyroid, growth rate and short stature

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11
Q

What is adrenarche?

A

onset of androgen dependent changes, e.g. pubic and axillary hair, BO, acne

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12
Q

What is thelarche?

A

onset of female breast development

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13
Q

What is puberty?

A

development of secondary sexual characteristics. Attain reproductive capacity

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14
Q

What is menarche

A

onset of menstruation

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15
Q

What factors influence the timing and onset of puberty?

A

genetic background
environment
general health of child

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16
Q

Definition of normal puberty

A

Girls- puberty development after the 8 years (mean 10 year)

Boys- puberty development after the age of 9 years (mean 12 years)

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17
Q

What are the clinical aspects of normal puberty?

A

Females: Breast development
Males: Genital development; testicular volume
Both: Pubic hair development
Axillary hair development

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18
Q

Describe the normal control of water balance

A

Stability of plasma concentration is controlled, in part, by hypothalamic centres that regulate thirst

Thirst mechanism- stimulates intake of free water and stimulates ADH release

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19
Q

Describe anti-diuretic hormone

A

Synthesised by the hypothalamus and stored in the posterior pituitary gland

Stimulates the distal and collecting tubules in the kidneys to increase the reabsorption of the free water into the cardiovascular system (maintains physiologic osmolality)

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20
Q

How does ADH work?

A

The hypothalamus senses low blood volume and increased serum osmolality and signals the pituitary gland

The pituitary gland secrets ADH into the bloodstream

ADH causes the kidneys to retain water

Water retention boosts blood volume and decreases serum osmolality

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21
Q

How does the nephron regulate fluid and electrolytes?

A

GLOMERULUS filters fluid at a rate of 180L/day
Acts as a bulk filter to pass along protein-free and red blood cell-free filtrate (liquid that has been filtered)

PROXIMAL TUBULE has freely permeable call membranes
Reabsorbs most electrolytes, glucose, urea and amino acids
Carries large amounts of water with electrolytes back to circulation
Reduces water concentration of filtrate by 70%

LOOP OF HENLE contains a high concentration of salts, mostly sodium
Further concentrates filtrate because of water lost by osmosis
Pulls chloride and sodium out of filtrate without water and reabsorbs them in ascending limb
Causes filtrate to become more dilute as it moves into distal tubule

DISTAL TUBULE reabsorbs water and concentrates urine as a result of antidiuretic hormone action
Reabsorbs sodium and water
Secretes potassium as a result of aldosterone action

COLLECTING DUCT has ADH which absorbs water
Absorbs or secretes potassium, sodium, urea, hydrogen ions, and ammonia, according to the body’s needs

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22
Q

What is plasma osmolality?

A

Measures the concentration of all chemical particles found in the fluid part of the blood
Normal levels 285-295mOsm/L

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23
Q

What is urine osmolality?

A

Used to measure the number of dissolved particles per unit of water in the urine
Normal levels 500-800mOsm/kg water
Large values = concentrated
Low values= dilute

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24
Q

What is diabetes insipidus?

A

An acute or chronic condition
Inadequate secretion of ADH from the posterior pituitary gland (cranial)
Insufficient renal response to adequate levels of ADH (nephrogenic) causes the kidneys to make a lot of urine
Causes in CDI- cerebral malformation
acquired disease
familial

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25
What do thyroid hormones effect?
Growth Neurological development Metabolism Cardiovascular function
26
What thyroid hormones are released by the hypothalamus?
Thyrotrophin Releasing Hormone (TRH)
27
What thyroid hormones are released by the pituitary gland?
Thyroid Stimulating Hormone (TSH)
28
What thyroid hormones are released by the thyroid gland?
Thyroxine (T4) | Tri-iodothyronine (T3)
29
What is the hypothalamo-pituitary adrenal axis?
Complex set of direct influences and feedback interactions Corticotrophin releasing hormone stimulates the release of adrenocorticotrophic hormone which releases cortisol which acts back onto the hypothalamus and pituitary
30
What are the layers of the adrenal gland?
``` OUTER LAYER (cortex) Zona glomerulosa (mineralcorticoids) Zona fasciculata (glucocorticoids) Zona reticularis (sex steroids) -All steroid hormones from cholesterol ``` ``` INNER LAYER (completely surrounded by cortex) medulla (catecholamines) ```
31
Outline the properties of the zona glomerulosa
Contains mineralcorticoids such as: | Aldosterone (regulated blood pressure by regulating salt retention)
32
What is hyperaldosteronism?
Due to excessive secretion of mineralcorticoids. Can cause excessive reabsorption of sodium chloride and water, causing increased blood volume and hypertension. Excess excretion of potassium, causing hypokalaemia, which leads to cardiac arrhythmias, alkalosis, syncope and muscle weakness
33
What is hypoaldosteronism?
A low amount of aldosterone results in failure of the kidneys to regulate sodium, potassium and water excretion, leading to - Blood sodium deficiency (hyponatraemia) and potassium excess (hyperkalaemia) - dehydration, low blood volume and low blood pressure
34
What is aldosterone?
Helps regulate the salt levels in the body: - Amount of salt intake varies with what we eat - The job of the kidneys is to prevent salt accumulation; this is to prevent increased blood pressure and fluid retention - Additionally they want to regulate and prevent salt loss which would cause vomiting and dehydration - Aldosterone makes the kidney conserve salt - If there is not enough salt in the diet, aldosterone production increases - If there is too much aldosterone amount is reduced
35
Describe the properties of the zona fasciculata
Produces glucocorticoids including cortisol | This is the body's natural steroid.
36
What are the 3 main functions of cortisol?
- Helps control blood sugar levels - Helps body deal with stress - Helps to control BP and blood circulation
37
Describe the properties of the zona reticularis
Produces sex steroids/androgens - DHEA (dehydroepiandrosterone) - Androstenedione (secondary sexual characteristics) - Produced by adrenal cortex in both sexes - Also produced by the testes in males - Adrenal androgens contribute to the formation of pubic hair
38
Describe the properties of the adrenal medulla
Produce catecholamines- ADRENALINE- Released in response to signals from the sympathetic nervous system Increases blood sugar, muscle glycogen breakdown, blood flow to muscle, respiration NORADRENALINE- Similar effects to adrenaline, as well as maintains BP DOPAMINE- Precursor to adrenaline and noradrenaline Is a neurotransmitter
39
What are the 2 categories of stressors?
Psychosocial and physical
40
What are some psychosocial stressors?
Bereavement, mental illness, work environment
41
What are some physical stressors
``` Heat/Cold Infection Bleeding Pain Fever Disease processes ```
42
What are the specific stressors in children?
Hunger Thirst Pain Fear
43
What are the 3 phases of the stress response?
Alarm (fight or flight) Resistance stage Exhaustion stage
44
Outline some of the effects of the alarm stage
- Fight or flight - Body responds immediately to a threat - Can be brief and short lived, or strong and longer lasting - Non essential activities are decreased (decreased blood supply and stimulation) What physiological effects take place? - Body organs and systems work together to increase the activity of organs that are most necessary in fighting off danger - Increase in blood supply to bring them increased oxygen and glucose
45
What are the examples of physiological responses of the alarm stage?
Pulse (Rate and strength) increase Respiratory rate and effort (increase) Blood pressure (increase) Body core temperature (slight increase) Skin (pales and cools and sweating occurs) Blood glucose concentration (increases) Urinary output (decreases, although bladder may relax) Mouth (dries) and digestive system (decreases digestive activity, stomach activity increases) Emotional state (sensation of fear, focus on stressor)
46
What happens to young infants in the alarm stage?
``` Dont usually sweat- not a useful indicator of stress Urinary output may vary Inability to communicate feelings Different stressors than adults Be familiar with vital signs for age ```
47
Describe the physiology of the alarm stage?
The hypothalamus is able to respond to the chemistry and composition of the blood as it passes through: e.g. toxins, fever, dehydration Receives nerve impulses from the conscious centres of the brain Triggers the SNS which... Activates the necessary organs and glands: Heart to increase Liver to produce glucose Spleen to release blood Stimulate adrenal medulla (adrenaline and noradrenaline) Posterior pituitary secretes ADH and decreases urine output
48
Describe the resistance stage
``` CORTISOL -Increases glucose -Increases protein breakdown -Blood vessels constrict -Decrease in inflammation. >Increases BP. May not be useful if no blood loss >Delayed wound healing >Increased risk of infection ``` ALDOSTERONE -Increases BP > Useful if bleeding or fluid loss has occurred or in dehydration but may be unhelpful Human GrowthHormone Thyroid hormones
49
Describe stress in infants
Young infants and especially preterm and low birthweight babies have immature body systems which alters their stress response - Poor thermoregulation-smaller changes in environmental or body temperature cause stress - Poor glucose stores- more likely to become hypoglycaemic (a stressor). Less glucose in the body to use during stress causes quicker exhaustion
50
Describe the exhaustion stage
- If the resistance stage is not successful in combating stress, the body will move to the exhaustion stage - Body mechanisms and reserves have been exhausted e.g. potassium levels fall dangerously low (lost to balance out sodium which is retained) and body cells cannot function normally- glucocorticoid production may be exhausted- cells and tissues do not receive necessary support - Body tissues, then whole organs start to fail - Unless urgent intervention occurs, this stage will prove fatal - Management should always aim to prevent the patient reaching the exhaustion phase - Young infants, and children who are not in good general health, will reach the exhaustion stage sooner than older children and those previously in good health
51
Describe the short-term stress response
Increased heart rate Increased blood pressure Liver converts glycogen to glucose and releases glucose into the blood Dilation of bronchioles Changes in blood flow patterns leading to increased alertness, decreased digestive system activity and reduced urine output Increased metabolic rate
52
Describe long-term stress responses
``` Retention of sodium and water by kidneys Increased blood volume and pressure Proteins and fats converted to glucose or broken down for energy Increased blood sugar Suppression of immune system ```
53
What is insulin?
Anabolic hormone which has a key role in glucose metabolism; has an important effect on fat and protein metabolism
54
What happens to insulin after eating?
Insulin rises, facilitating entry of glucose into cells via glucose specific transporters (especially in muscle and adipose tissue) Insulin stimulates glycogen synthesis in the liver and muscles
55
What happens to insulin during fasting?
Glucose concentration and insulin secretion fall Absence of glucose uptake in muscle and adipose tissue Stimulation of glycogenolysis in the liver and muscles, and hepatic gluconeogenesis, from amino acids and ketones
56
Describe glucose regulation
``` The pancreas has an exocrine and endocrine function Pancreatic islets (islets of Langerhans) are clusters of cells and this is the endocrine part of the pancreas Pancreatic islets consist of beta cells which secrete the hormone insulin and alpha cells which secrete the hormone glucagon ```
57
Describe the difference between insulin and glucagon
Insulin- decreases glucose | Glucagon- increases glucose
58
Describe the release of insulin
Release stimulated by high blood sugars. Insulin acts on different cells, especially liver and skeletal muscle cells to promote the facilitated diffusion of glucose into the cells Insulin speeds up the synthesis of glycogen from glucose (glucose stored as glycogen in cells) Blood glucose levels falls as glucose diffuses out of the blood into the cells where it is stored as glycogen Insulin release is inhibited by a low blood sugar (negative feed back)
59
Describe the release of glucagon
Is stimulated by low blood sugars; in order to increase them. It acts on liver cells to promote breakdown of stored glycogen back into glucose Liver releases this glucose into the blood so blood glucose level rises Glucagon release is inhibited by high blood glucose levels (negative feedback)
60
Describe insulin-dependent diabetes mellitus in children
``` It is an autoimmune destruction of the beta cells in the islets of langerhans in the pancreas. This means it will not produce the insulin needed to break down blood sugars. Without insulin, blood glucose cannot enter cells therefore more and more builds up in the blood causing high blood sugars. Occurs in 1 in 400/500 children and adolescents Persistent hyperglycaemia (fasting blood glucose >7mmol/L) Serious risk of diabetic ketoacidosis Risk of long term complications such as retinopathy, renal failure, cardiovascular disease, neuropathy ```

Biosciences 2 (5 decks)

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