9. ENDOCRINE SYSTEM Flashcards
The structure and function of the endocrine system. The clinical presentations, investigation procedures and some orthodox treatments of endocrine pathologies.
What stimulates the production of thyroid hormones?
TSH, exercise, stress, malnutrition, insulin & growth hormone
Define ‘metabolic rate’
The sum of all chemical processes in our cells.
What reduces thyroid hormones in the body?
Low TSH, high T3
Which gland in the body produces melatonin?
Pineal gland
Describe the main function of the endocrine system
The endocrine system coordinates the activity of organs through hormones (chemical messengers released into the blood by glands that produce them).
Name four endocrine tissues
Adipose tissue
Heart
GIT
Liver
Kidneys
Skin
Placenta
Name two ways in which hormone secretion is regulated
- Nervous system signals
- Chemical changes in the blood
- Other hormones
Explain how the hypothalamus and the pituitary gland are connected
The anterior lobe of the pituitary is connected to the hypothalamus through a network of blood capillaries while the posterior lobe is connected through a stalk of nerve fibres.
What is Hashimoto’s Thyroiditis?
An autoimmune condition of thyroid hormone deficiency caused by the body’s immune system attacking the thyroid
List four key symptoms of Hashimoto’s Thyroiditis
Tiredness, Weight gain, Constipation, Depression, Cold intolerance
What would you expect blood tests to reveal in Hashimoto’s?
High TSH
Low thyroid hormones (T4 and T3)
Name four nutrients that are essential for the synthesis of thyroid hormones
Iodine
Selenium
Tyrosine
Zinc
What are two signs of hypothyroidism?
Goitre Myxoedema Loss of eyebrows Thin hair Dry, brittle skin
Name two endocrine glands
- Pituitary
- Thyroid
- Adrenals
Describe ‘down regulation’ and name one example
Down regulation occurs if a hormone is present in excess. This means that the number of target cell receptors for that hormone may decrease. An example of this is the hormones that increase during puberty.
Describe ‘up regulation’ and name one example
A deficiency in a certain hormone causes an increase in the number of receptors on target cells. This occurs when there is an increased number of oxytocin receptors in third trimester of pregnancy.
Explain the difference between receptors for protein-based hormones and lipid hormones.
The receptors for protein-based hormones are part of the cell membrane, whilst lipid hormone receptors are within the cell.
With regards to hormones released from the hypothalamus, name:
a. Three releasing hormones
b. Two inhibiting hormones
a. GHRH (Growth Hormone Releasing Hormone) TRH (Thyroid Releasing Hormone) PRH (Prolactin Releasing Hormone) GnRH (Gonadotropin Releasing Hormone) CRH (Corticotropin Releasing Hormone)
b. GHIH (Growth Hormone Inhibiting Hormone)
PIH (Prolactin Inhibiting Hormone)
Name two hormones that are released by the posterior pituitary gland
Oxytocin Antidiuretic Hormone (ADH)
Name one hypothalamic hormone that stimulates the release of both ACTH and MSH.
CRH (Corticotropin Releasing Hormone)
Name two functions for each of the following anterior pituitary hormones:
a. Growth Hormone
b. ACTH
c. Prolactin
a. Growth Hormone: Growth and repair; Metabolism
b. ACTH: Circadian Rhythm; Steroid hormone output
c. Prolactin: Milk production (with oxytocin); prevents pregnancy; breast maturation
Name two factors that stimulate production of the following hormones:
a. Growth Hormone
b. ACTH
c. Prolactin (not birth)
a. Growth Hormone: Night time, hypoglycaemia, exercise, childhood/adolescence
b. ACTH: hypoglycaemia, exercise, stressors (eg. emotions, fever), interleukin-1 (inflammatory cytokine)
c. Prolactin: suckling of infant, sleep
When are TSH levels at their
(a) Lowest
(b) Highest
(a) During early evening
(b) During the night
Name one function of melanocyte stimulating hormone (MSH)
It plays a role in skin, hair and eye pigmentation
Name TWO functions of oxytocin
- It contracts the uterus in childbirth
- It contracts the lactating breast
- It is a bonding hormone (mother with baby, social bonding, trust, skin contact, ‘cuddle hormone’).
List TWO factors (not suckling) that stimulate oxytocin production
- Childbirth
- Skin to skin contact / cuddles
What is colostrum?
The first breast-fluid produced after parturition, which contains water, lacto-sugar and antibodies
Describe the main function of colostrum
Coslostrum acts as a laxative to encourage bowel movement, particularly bilirubin and wastes that have accumulated in the foetal intestines.
Describe how ADH prevents loss of fluid from the body
ADH reduces urine output by stimulating reabsorption of water from the kidneys and vasoconstriction in skin lowers loss of water through sweating.
Name ONE factor that:
a. Stimulates production of ADH
b. Inhibits production of ADH
a. Increased osmotic pressure, hypovolaemia
b. Reduced osmotic pressure, alcohol, increased fluid intake
Using definitions, explain the difference between acromegaly and gigantism
Acromegaly is the result of excess growth hormone post puberty while Gigantism is an excess of growth hormone while the bones are still developing (pre-puberty onwards)
List TWO signs / symptoms of acromegaly
- Large, prominent facial features, large hands and feet
- Tiredness
- Deep voice
- Impotence
- Joint pain
- Bone deformities
- Soft-tissue swellings
Explain why Type 2 diabetes is a potential complication of acromegaly and gigantism
Excess growth hormone leads to increased blood glucose levels which can lead to insulin resistance
Name the following pathology and list ONE cause:
“Galactorrhoea, amenorrhoea, decreased libido / sexual dysfunction and sub-fertility”
Hyperprolactinaemia.
Pituitary tumour, acromegaly, pharmacologic (antipsychotics)
What is meant by galactorrhoea?
The flow of milk from the breast not associated with childbirth.
Using definitions describe the difference between diabetes insipidus and Type 2 diabetes
Diabetes insipidus is the deficiency of ADH production or recognition, causing the kidneys to over-excrete water.
Type 2 diabetes is a metabolic disorder associated with hyperglycaemia, characterised by a deficiency of insulin due to insulin resistance.
List TWO causes of diabetes insipidus
- Cranial: brain trauma, tumour, encephalitis
- Renal: Chronic kidney disease, hypercalcaemia, hypokalaemia
Name TWO signs / symptoms of diabetes insipidus
- Polydipsia (extreme thirst), high water consumption
- Polyuria (excessive urine output)
- Weight loss
- Low blood pressure, syncope
With regards to diagnostic tests for diabetes insipidus, describe what you would expect to find with:
a. Urine volume over 24 hours
b. Urine concentration (urine specific gravity)
c. Sodium levels (blood biochemistry)
a. Higher than normal volume
b. Low, urine being more diluted than normal
c. High sodium levels in urine
State which gland produces melatonin
Pituitary gland
Describe how age affects melatonin levels
Melatonin levels decline with age
Name ONE factor that stimulates melatonin
Darkness
Name TWO factors that reduces melatonin levels
Daylight
Irregular sleep patterns (night-shifts)
State TWO functions of melatonin
- Sets the circadian rhythm
- Potent antioxidant
With regards to iodine atoms, describe the difference between thyroxine and triiodothyronine
Thyroxine has four iodine atoms while triiodothyronine has three iodine atoms
Name the thyroid cell which store the following:
a. Iodine
b. Calcitonin
a. Follicular cells
b. Parafollicular cells
Name ONE amino acid needed for production of thyroid hormones
Tyrosine
Name TWO minerals which are essential for the conversion of T4 to T3
Selenium and Zinc
Name the most biologically-active thyroid hormone
T3 (Triiodothyronine)
Describe how thyroid hormones are measured
Thyroid hormone levels are measured in terms of free T4 and T3
State TWO functions of thyroid hormones
- Thyroid hormones increase metabolic rate and heat production.
- They are essential for normal growth and development as well as CNS function.
- They work in conjunction with adrenaline, noradrenaline, insulin and growth hormone.
List TWO factors that:
a. Stimulate thyroid hormone production
b. Reduce thyroid hormone production
a. TSH; exercise; stress; malnutrition; low blood glucose; low T3 to T4
b. Low TSH; high T3
Explain why TSH levels are measured in the morning
TSH levels are measured in the morning as it is the highest and most reliable / consistent value.
Name ONE antibody used to identify autoimmune thyroid disease
Anti-thyroglobulin antibodies (TgAb)
List TWO signs of hypothyroidism
Goitre Myxoedema Dry, brittle skin Thin hair Loss of eyebrows
List FOUR symptoms of hypothyroidism
Tiredness Malaise Weight gain Cold intolerance Constipation Depression
Name TWO causes of hypothyroidism
- Hashimoto’s thyroiditis (autoimmune)
- Iodine deficiency
- Fluoride
- Thyroid destruction (surgery, radioactive iodine, tumour, medications)
Define Grave’s disease
Grave’s is hyperthyroidism and is characterised by hyper-metabolism and elevated serum levels of free thyroid hormones (also know as thyrotoxicosis).
Describe the pathophysiology of Grave’s disease
Increased IgG antibodies bind to TSH receptors and stimulate production of thyroid hormones.
List FOUR signs / symptoms of Grave’s disease
Nervousness Irritability Hyperactivity Unexplained weight loss Muscle weakness Heat sensitivity Goitre Exopthalmos
Describe in detail how blood calcium levels are affected by the following hormones:
a. Calcitonin
b. Parathyroid hormone
a. Produced by the parafollicular cells of the thyroid gland and lowers blood calcium by inhibiting calcium reabsorption from the bone and kidneys and inhibiting osteoclast activity.
b. Produced by the parathyroid and increases blood calcium by increasing osteoclast activity, increasing kidney reabsorption of calcium and magnesium and increasing production of calcitriol which increases calcium absorption in the GIT.
Name TWO signs / symptoms of hyperparathyroidism
Hypercalcaemia (risk of kidney stones, osteoporosis or osteopenia, low energy and depression)
Nausea, vomiting, constipation, anorexia, muscle paralysis
Name TWO signs / symptoms of hypoparathyroidism
Hypocalcaemia (muscle cramps and spasms, tingling lips, fingers and toes, dry hair, brittle nails, dry scaly skin, cataracts, weakened tooth enamel in children)
Name TWO hormones produced by the adrenal cortex
Cortisol (a glucocorticoid)
Aldosterone (a mineralocorticoid)
Androgen (sex hormone)
State the main function of adrenaline and noradrenaline
Both adrenaline and noradrenaline intensify the sympathetic response.
Name TWO factors that stimulate adrenaline and noradrenaline
Exercise Fasting Shock Elevated temperature Emotional stress Caffeine Infection Disease
Name TWO factors that inhibit adrenaline and noradrenaline
Eating
Sleeping
Calmness
Diaphragmatic breating
Name FOUR functions of cortisol
- Stimulates gluconeogenesis
- Proteolysis (amino acids from protein)
- Lipolysis
- Production of glucose by the liver
- Reduces immune response and tissue repair
- Anti-inflammatory
- Weak reabsorption of sodium and water from kidney
State TWO functions of aldosterone
- Maintains the water and electrolyte balance by:
1. Stimulating reabsorption of sodium in the kidneys
2. Causing retention of water in the kidneys to increase blood volume and pressure
3. Stimulating excretion of potassium in urine
Name ONE factor that stimulates aldosterone production
- Low blood pressure or blood volume
- High blood potassium
Name ONE factor that inhibits aldosterone production
Low blood potassium
Using definitions, explain the difference between Cushing’s syndrome and Addison’s disease
Cushing’s syndrome is an excessive amount of glucocorticoids (hypercortisolaemia)
Addison’s disease is due to hypo-functioning of the adrenal cortex, causing a deficiency of mineralocorticoids and glucocorticoids.
Name TWO causes of Cushing’s syndrome
- Corticosteroid therapy
- Adrenal ademoma
- Pituitary adenoma (Cushing’s disease)
List THREE signs / symptoms of Cushing’s syndrome
- Central weight gain
- Moon face
- Buffalo hump
- Insulin resistance
- Abdominal stretch marks
- Easy bruising
List ONE cause of Addison’s disease
- Atrophy of the adrenal glands (85% autoimmune)
- Secondary to a disease or abrupt cessation of steroids
List TWO signs / symptoms (not skin pigmentation) of Addison’s disease
- Weakness
- Fatigue
- Hypotension
- Muscle weakness
- Increased thirst
- Malaise
- Depression
- Impotence / amenorrhoea
Explain why hyperpigmentation occurs in Addison’s disease
Adrenal failure leads to a lack of adrenal hormone production and a breakdown of the normal negative feedback mechanism. The hypothalamus produces an excess of corticotrophin releasing hormone (CRH), which causes the pituitary to erroneously produce melanocyte stimulating hormone which causes the skin to darken.
Explain what is meant by ‘Addison’s crisis’ and name ONE characteristic sign / symptom
a
Name TWO functions of androgens
a
List ONE factor that stimulates androgen production
a
Describe the difference between ‘alpha cells’ and ‘beta cells’ in the pancreas
a
State the normal blood glucose range
4-7mmol/L
Name TWO functions of insulin
a
Name TWO factors that:
a. Stimulate insulin production
b. Inhibit insulin production
a.
b.
List ONE function of glucagon
a
Name TWO factors that:
a. Stimulate glucagon production
b. Inhibit glucagon production
a.
b.
Using definitions compare Type I diabetes with Type 2 diabetes
a
Name ONE cause of secondary diabetes
a
Which type of diabetes is a woman with gestational diabetes at higher risk of developing post childbirth?
a
State TWO dietary causes of Type I diabetes
a
Name ONE viral cause of Type I diabetes
a
List THREE signs / symptoms of Type I diabetes
a
State TWO lifestyle factors that contribute to the development of Type 2 diabetes
a
Name TWO diagnostic tests for identifying diabetes mellitus
a
Name THREE complications of diabetes mellitus
a
Describe specifically how ketoacidosis develops
a
Name FOUR signs / symptoms of hypoglycaemia
a