The Endocrine System Flashcards
Where can organs of endocrine system mainly be found?
Neck Head Thoracic cavity Abdomen Pelvic cavity
What two things can secrete hormones.
Organs
Glands
Describe exocrine glands and examples
Exocrine glands have a duct and secrete products directly onto a surface or within a cavity through it
Examples: Salivary glands secrete saliva into mouth
Sweat glands secrete sweat onto skin surface
Describe endocrine glands and examples.
Endocrine glands are ductless. They secrete their hormone into extra cellular fluid which diffuses into blood. It is then carried through blood to bind to a specific receptor on target cell or organ. This triggers a reaction.
Eg. Pituitary, adrenal and thyroid gland
What organs can produce hormones
Pancreas
Liver
Heart
Do hormones excite or inhibit
They excite or inhibit activity of other organs or tissues
What hormones are produced by stomach?
Gastrin
Hormones produced by small intestine:
Peptides
Secretin
Cholecystokinin
Hormones produced by kidney
Erythropoietin
Renin
1,25- DHCC
5 Main functions of the endocrine system
Balances sodium and water for blood volume
Balances calcium and phosphate levels to preserve extra cellular fluid for cell survival
Balances energy and controls macronutrients - proteins, carbohydrates and lipids and how they’re used and stored
Responses to stress
Reproduction, growth and development and sexual development
What are categories of hormones
Non steroidal
Steroidal
What do non steroidal hormones do?
They are one amino acid or short chain of amino acids. They bind to specific receptors on cell membrane, by lock and key.
Many chemical reactions happen once it has bind to activate molecules in the cell
These reactions are secondary messengers
Secondary messengers cause further reactions, secrete more hormones or secrete a different hormone
What do steroidal hormones do?
Small, lipid soluble chemicals. Pass through cell membrane and easily through the cytoplasm.
They can enter nucleus of cell to bind to a receptor within the nucleus
Hormone-receptor complex formed
Complex causes DNA to do different things - eg, speed or slow cell processes, enable transport into cell or cell to secrete something else
Which type of hormone is quicker response?
Non steroidal hormones act quicker than steroidal
What are non steroidal hormones soluble in?
Soluble in water and insoluble in lipids
What are the two types of non steroidal hormones?
Peptide or protein hormones
Amino - acid derived hormones
Describe peptide or protein hormones
Most of non steroidal are this type
Vary in size (3-200 amino acids long)
They are synthesised as pre-prohormones first then undergo transformation to functioning hormone
Stored in secretory glands and exocytose from the cell
Examples: Insulin, glucagon and adrenocorticotropic hormones
Amino acid derived
These proteins are synthesised from another amino acid
Commonly end in ‘ine’
Eg, adrenaline , noradrenaline and dopamine
Steroidal hormones
Lipid soluble molecules
Derived from cholesterol and produced in adrenal cortex, gonads and placenta in women
Require binding proteins in the blood
Examples- Testosterone, oestrogen and progesterone
5 Major pathways for hormones
PASEN
Paracrine- Cell produces and secretes a hormone and the hormone acts directly on nearby cell, eg, histamine and bradykinin
Autocrine- Cell produces and secretes hormone then the hormone binds to receptors on the cell membrane of the cell it came from, so these cells are secretory and receptive cells!
Synaptic pathway- Hormones produced in neurone, secreted and travels along axon to a synapse, where they are released and taken up by nearby neurone to exert effect.
Endocrine/ telocrine - hormone produced and secreted from cell, travels through blood and binds to distant cells at receptors
Neuroendocrine- Hormone produced in neurone, secreted, travels along axon to synapse, released and taken up into blood vessels to travel to cells with specific receptors
Where are hypothalamus and pituitary gland?
Near each other at base of brain
How do hypothalamus and pituitary gland interact?
Hypothalamus has neurones that produce inhibiting and releasing hormones to act on pituitary gland
Give four common releasing hormones from hypothalamus
GHRH- Growth hormones releasing hormone
TRH- Thyrotropin releasing hormone
CRH- Corticotropin RH
GnRH- gonadotropin RH
What does GHRH do?
Growth hormone RH released from hypothalamus and stimulates pituitary gland to produce growth hormone
What does TRH do?
Thyrotropin RH released from hypothalamus and stimulates pituitary gland to produce thyroid stimulating hormone
CRH?
Corticotropin RH comes from hypothalamus and stimulates pituitary gland to produce adenocorticotropic which releases cortisol in stress
GnRH
Gonadotropin release hormone from hypothalamus stimulates pituitary gland to produce reproductive hormones
What is the hormone known as that comes out of pituitary gland?
The TROPIC hormone
What may trigger hypothalamus and pituitary gland to release hormones?
Neurotransmitters
Injury
Release of chemical mediators from injury
Neuroendocrine signals
They provide input to hypothalamus to regulate bodily functions
Negative and positive feedback systems
negative feedback loop
Most common mechanism
Influenced by environmental and body temp, stress, nutrition and body substances
Eg thyroid hormone or insulin in glucose regulation
Example of negative feedback
Eating lots of carbohydrates - broken down to glucose
Glucose levels rise
Detected by beta cells in pancreas
Stimulates release of insulin
Insulin unlocks cells to absorb glucose
As glucose enters cells, blood glucose decreases
Pancreas stops producing insulin as it isn’t needed any more
Positive feedback loop
Less common
Amplify changes rather than reverse them
Presence of hormone stimulates increased production of hormone until cycle is interrupted
Eg oxytocin in childbirth
Oxytocin
In birth, cervix is stretched and stimulates oxytocin release from hypothalamus
More oxytocin means stronger and faster contractions
Cervix stretched even more as more oxytocin produced and baby pushes
Contractions stronger and faster until baby born
Cervix no longer stretched
Hypothalamus stops producing oxytocin
Causes of altered hormone function
Impairment of pituitary gland or hypothalamus
Impairment of endocrine glands
Inactive hormone produced by gland
Too much or too little hormone produced
Inadequate hormone receptor binding
Lack of response from target cell when hormone binds - lock and key does not work
Impaired negative feedback loop
Hormone produced in wrong place
Impaired hormone metabolism and elimination
What is acromegaly ?
Body produces too much growth hormone in adulthood
Usually due to a benign tumour on pituitary gland
Adults have large features so large hands and feet, enlarged tongue and prominent facials features
Susceptible to carpal tunnel syndrome
Gigantism
Body produces too much growth hormone during childhood
Problem with pituitary gland, usually tumour
Child appears large all over - very tall, large hands and feet and facial features. Prominent jaw and forehead.
Achondroplasia/ dwarfism
Too little growth hormone produced from pituitary gland
Short arms and legs and normal size torso
Genetic disorder
Name some other endocrine disorders
Hyperthyroidism (grave’s disease)
Immune system will attack and damage thyroid gland cells
Hypothyroidism (goitre, myxedema and developmental delay in children)
Cushing syndrome
Diabetes mellitus / insipidus
Pheochromacytoma
Glucagonoma
Somatostatinoma
What is thyroid like and what does it do?
Butterfly shape gland at anterior neck - shouldn’t be seen or able to palpate
Critical role in metabolism
Facilitates breakdown of proteins, carbohydrates and lipids for energy, stimulates heat and produces glucose
Produces other structural proteins, enzymes or hormones
Promotes growth and development in children mentally and physically
Thyroid hormones
Thyrotropin RH comes from hypothalamus and stimulates thyroid hormone to produce thyroid stimulating hormone
Thyroid stimulating hormone makes us release other thyroid hormones =
T4= Thyroxine / tetraiodothyronine
T3= Triiodothyronine
Thyroid hormones also send signals to hypo and pituitary
Issues with thyroid may have temperature or stress symptoms
Thyroid hormones being released causes what? 10
Increased glucose absorption
Increased oxygen consumption
Increased cardiac output
Release of lipids from adipose
Increased cholesterol breakdown in liver
Increased gastric motility
Increased body heat production
Metabolism of proteins from muscle tissue
Increased muscle tone and reactivity
Increased activation of cognitive processes
Define hyperthyroidism
A disease where too many thyroid hormones are produced
What causes hyperthyroidism?
Increased stimulation of thyroid gland
Disease of thyroid gland
Increased production of thyroid stimulating hormone by pituitary tumour
Medications with high levels of iodine - eg cough medicine
Health supplements or vitamins containing seaweed (high in iodine)
Define hypothyroidism
Too little thyroid hormones produced from thyroid- congenital or acquired
Describe congenital hypothyroidism
Occurs in foetal development
There is lack of thyroid development so lack of thyroid hormones produced
In Utero maternal T4 crosses placenta and baby appears normal at birth as they’ve grown and developed using mothers T4
Once cord is cut, there is gradual decline in growth and developmental delay as baby doesn’t produce own T4- has hypothyroidism
Baby needs T4 supplement - sometimes picked up too late and can’t be given T4 as they’ve already missed brain development so is life shortening
If detected by neonatal screening, or blood test, thyroid replacement treatment is given
Graves’ disease
Auto immune disease causing excessive stimulation of thyroid gland
7-10 X more common in women than men
They think it is caused by immunoglobulin antibodies that bind to TSH receptors on thyroid is too many thyroid hormones produced
We get thyrotoxicosis= too many thyroid hormones in blood
Symptoms: Enlarged thyroid gland (goitre so swelling anterior neck)
Higher metabolic rate
Weight loss Agitation they can’t explain Sweating profusely Tachycardia Intolerant to heat Palpitations Tremor Fine hair everywhere Menstrual cycle problems Exophthalmos (bulging eyeballs) Weakness (as metabolism really high)
Treatment - quick treatment to prevent appearance like this
Medication to stop thyroid hormone production
Radio iodine treatment where radiotherapy destroys thyroid cells
Surgery to remove part or all of thyroid
Whole taken Away = supplements needed
Acquired hypothyroidism
Thyroid gland doesn’t produce enough thyroid hormone
Due to: Autoimmune disorder Iodine deficiency Surgical removal of thyroid gland Radiotherapy to thyroid gland Medications that destroyed thyroid gland
10 X common in women than men
Treatment : lifelong replacement hormone treatment
Eg, levothyroxine gives synthetic version of T4
Alleviation if clinical signs like constipation meds and fertility assistance
Symptoms: Fatigued / lethargic Cold all the time Weight gain Dry skin Coarse hair Constipation Reproduction - fertility problems Memory problems Goitre- thyroid trying to produce more hormones so increases in size Protein- carbohydrates disturbance so appear boggy Oedematous tissues like hand, feet and face Myxoedema Skin boggy and soft
