Endocrine System- All notes Flashcards
What are the types of intercellular messenger system?
-neurotransmission, neuroendocrine, endocrine, paracrine and autocrine
What is the endocrine system?
-Gland in the system secretes a neurotransmitter which gets released into he bloodstream to travel to the target cell
What are the features of hormones?
-glands that secrete them directly into the bloodstream to be carried to target cells or tissues away from the endocrine gland
What are the types of hormone?
-Peptide, steroidal, tyrosine containing and eicosnaoids
What are the differences between types of hormones?
-Structural (chemical) difference change the synthesis, storage, transportation and biological functions of hormones
What are peptide hormones?
-Chains of an amino acid that can be small or larger and are mostly secreted from the hypothalamus, pituitary gland, pancreas and GIT
What is the synthesis of peptide hormones ?
-Similar to any protein syntesis; transcription / translation- preprohormone-prohormone-hormone-secretory glands
Where are peptide hormones stored?
-Within the vesicles in the cell
How are peptide hormones release?
-Exocytosis
How are peptide hormones transported?
-They are hydrophilic so freely circulate in the blood vessel, no plasma protein bonding so short half-life
What are steroidal hormones?
-Hormones that have cholesterol as the base e.g. cortisol and sex hormones
How are steroidal hormones synthesised?
-Enzymatic conversion of precursor (cholesterol base) molecules into hormone
How are steroidal hormones released into the bloodstream?
-Stimulus increased precursor level and enzyme activation so molecules simply diffuse across membrane and bind with plasma protein until needed
How are steroidal hormones transported?
-Travel in the bloodstream joined with a a carrier protein in an inactive state until it is needed and released. Lipophilic so has a hard life of hours to days
What is a tyrosine containing hormone?
-A hormone that has tyrosine as the base such as thyroid hormones
How are tyrosine containing hormones released?
-Stimulus required then simple diffusion across membrane
How are tyrosine containing hormones transported ?
-Lipophilic, binds with a plasma protein in the blood with weak reversible bonds to give a half life of hours to days
What are eicosanoids?
-Hormones that are synthesised by stereo- and regional’s-specific peroxidation of arachidonic acid (membrane lipid) as the precursor and lipase as the enzyme that dictates production
How are eicosanoids released?
-Stimulus required as poorly diffuse across cell membrane
How are eicosanoids transported?
-Required an anionic transporter. Hav a half life of seconds and is limited to autocrine and paracrine effects
How do peptide hormones function?
-Hormones interact with the cell surface receptors which then stimulates a response inside the cell which leads to a physiological response
How do steroidal hormones work?
-They are diffused across the cell membrane or even into the nucleus to interact with either a cytosolic or nuclear receptor which then produces specific protein and biological effects
How are hormones metabolised?
-Enzymes in the liver, blood and kidney then excreted in the urine
How does the negative feedback axis of hormonal homeostasis work?
-Endocrine glad releases a hormone which acts directly on target cells. If the target cell is receiving too much or too little hormone, it will send a message to the gland to reduce or increase production
How does the hypothalamus pituitary axis work?
-Hypothalamus relates CRH which acts on the anterior pituitary gland which releases trophic hormone ACTH which acts on peripheral endocrine gland which produces cortisol which acts on target cells
How is the hypothalamus -pituitary axis regulates?
-Feedback loop can go back to any point in the axis to increase or decrease production of certain hormone
Why is the sleep/wake cycle clinically significant when testing for hormone levels?
-Hormone levels will naturally fluctuate significantly within the sleep/wake cycle so depending on the time of day, certain hormones will be higher or lower than normal
What happens if the …. is hyper secretion in hypothalamus -pituitary axis?
-Type 1 diabetes
What is a primary defect in hypothalamus -pituitary axis?
-Anything wrong with the PEG
What is a secondary defect in hypothalamus-pituitary axis?
-Senses there is not enough cortisol as PEG isn’t producing any so produces more ACTH that can not be used
What can you deduce if there is too much ATCH in blood?
-Issue with PEG
What are some causes of hyper secretion?
-Tumour or Immunological
What are some causes of hypo secretion?
-Genetic, immunological, destruction of gland by disease or trauma
How can you diagnose an endocrine disorder?
-Signs and symptoms, hormone levels (bloods), imaging
What test would you do if you suspect hyposecretion?
-Stimulation tests
What test would you do if you suspect Hypersecretion ?
-Suppression tests
How would you treat hyposecretion?
-Replace the hormone through supplements (insulin)
How would you treat hyper secretion?
-Block the synthesis and release using drugs
How would you treat impaired target-cell responsiveness?
-Drugs to enhance cellular response to hormone
What is the function of the anterior pituitary ?
-Controls the release of anterior pituitary hormones by passing releaasing factors along the portal vessels
What are the anterior pituitary hormones?
-Growth Hormone (GH), Thyrotropin (TSH), Prolactin (PRL), Adrenocorticotropic hormone (ACTH), gonadotropins (LH, FSH)
What is the function of the posterior pituitary gland?
-Stores paraventricular (PVN) and supraoptic (SON) nuclei and neurons carrying oxytocin and ADH
What does tropic mean?
-Turning, affecting the activity of an endocrine gland
What does trophic mean?
-Feed, promotes growth and tissue integrity
If GHRH is the hypothalamus-releasing hormone, what would happen next?
-Anterior pituitary would release growth hormone which would go to long bones and big muscles to stimulate growth
If Gonadotropin-releasing hormone is the hypothalamus - releasing hormone, what would happen next?
-FSH and LH would be released from anterior pituitary and in males LH makes testosterone in testes and FSH controls sperm production and in females they both work together to control the menstrual cycle
If corticotropin-releasing hormone is the hypothalamus-realising hormone, what would happen next?
-Anterior pituitary will release adrenocorticotropic hormone (ACTH) which will travel to adrenal glands causing them to release cortisol and regulate metabolism and the immune response
If thyrotropin-releasing hormone is the hypothalamus-releasing hormone, what would happen next?
-Anterior pituitary will release thyroid-stimulating hormone (TSH) which will travel to the thyroid gland and stimulate the release of thyroxine
If dopamine (inhibition) is the hypothalamus-releasing hormone, what would happen next?
-Prolactin will be released from the anterior pituitary and travel to the breast tissue to stimulate milk production ?
What are the features of somatotropin (GH) ?
-Secreted by acidophilic cells of anterior pituitary, stored as granules, is a peptide hormone
What is GHs direct function?
-Effects metabolism by increasing blood glucose, gluconeogenesis, protein synthesis and lipolysis and decreasing glucose uptake
What are somatomedins or IGFs?
-Insulin like growth factors from the liver
What are somatomedins or IGFs?
-Insulin like growth factors from the liver
What are the indirect functions of GH?
-Increased protein synthesis (cell size), cell division (cell number) and skeletal growth
What affects GH release?
-Blood glucose, free fatty acids, amino acid levels , sleep, exercise and age
What are the symptoms of dwarfism caused by lack of GH?
-Psychological changes, malaise, tiredness, osteoporosis, poor muscular tone, impaired hair growth and increase is adipose tissue
What are the symptoms of giantism (in children)/ acromegaly (in adults)?
-Coarsening of facial features, enlarged hands and feet headaches, sleep apnoea, hypertension, diabetes, issues with periods or impotence
What are the thyroid hormones ?
-Thyroxine (T4), Tri-iodothyronine (T3), calcitonin and parathyroid hormone (PTH)
What is mono-iodotyrosine?
-Tyrosine iodinated at 3’ of ring
what makes up thyroxine (T4)?
-Two di-iodotyrosine
What makes up trip-iodothyronine (T3)?
-One MIT and one DIT
What is calcitonin?
-Produced by parafollicular C cells and acts to reduce plasma calcium
What is PTH?
-Produced by parathyroid glands on the posterior surface of the thyroid gland to increase plasma calcium and oppose calcitonin effect
What are the functions of T3?
-4B’s increases:
-Brain maturation
-Bone growth
-Beta-adrenergic effects
-Basal metabolic rate
What is goitre?
-Enlargement of the thyroid gland
What are the symptoms of hyperthyroidism in relation to the 4Bs?
-increased temp, weight loss, diarrhoea, anxiety, restlessness, tremor, growth acceleration, increased HR and MAP leading to palpations
What are the symptoms of hypothyroidism in relation to the 4Bs?
-Decreased body temp, cold intolerance, weight gain, constipation, depression, confusion, poor memory, growth deficiency (children), HR and MAP leading to hypotension
What is graves disease?
-A cause of hyperthyroidism where thyroid stimulating immunoglobulins (TSI) activate the thyroid gland to produce and release thyroid hormones. Symptoms include nervousness, weight loss tremor, sweating, heat intolerance and goitre
What is prolactinoma?
-Excess or hyperprolactinaemia can cause loss of fertility or libido
What are the hormones of the adrenal gland ?
-Aldosterone, cortisol, adrenaline and dehydroepiandrosterone
What effect do the zones of the adrenal cortex have on the hormones?
-Have different enzymes that change the structure of cholesterol to produce different hormones
What are the features of aldosterone?
-Increases sodium and water reabsorption and potassium excretion in the urine. Stimulated by increased plasma [K+]
What are the symptoms of hypoaldosteronism ?
-Hyperkalemia
-Hyponatremia
-Hypotension
-Hypovolemia
What are the symptoms of hyperaldosteroism?
-Hypertension
-Hypervolemia
-Hypernatremia
-Hypokalemia
What are the features of androgens ?
-DHEA are steroid hormones regulating the development and maintenance of male characteristics secreted by the level of ACTH
What are the symptoms of hypoandrosteronism?
-Loss of energy, erectile dysfunction , libido, loss of muscle and bone mass
What are the symptoms of hyperandrosteronism?
-Excess hair and masculinisation-more predominant in females
What is a disease caused by excess cortisol?
-Crushings syndrome
What are the symptoms of crushing syndrome ?
-Round Face, Reddened Cheeks, Weight Grain, Central obesity, Buffalo Hump, Easy brushing, fatigue
What is a disease caused by insufficient adrenal cortisol?
-Addison’s disease
What are the symptoms of Addisons disease?
-Hair loss, blurred vision, abdominal pain, decreased appetite, weight loss, hypoglycaemia
What are the features of ADH and arginine vasopressin (AVP) ?
-Stimulated by hypovolemia, hypersmolality and hypotension. Stimulate ACTH release, vasoconstriction and increase permeability for reabsorption of water
What happens if there is a lack of ADH and AVP ?
-Diabetes insipidus (DI): polyuria and polyuria and polydipsia
-Pituitary DI: inadequate release of ADH secretion (SIADH), CNS pathologies, malignancy, water retention, concentrated urine
What are the features of oxytocin?
-Positive feedback axis, stimulates expression of breast milk, uterine smooth muscle contraction, maternal/sexual behavioural
Name the three enzymes that are involved in insulin?
-Proconvertase 1 (PC1)
-Proconvertase 2 (PC2)
-Carboxypeptodase H (CPH)
