Endocrine system Flashcards
What are the 8 endocrine glands?
Pituitary gland
Pineal gland
Thyroid gland
Thymus gland
Adrenal gland
Pancreas
Ovaries
Testis
What are hormones?
Chemical signals produced in endocrine glands or tissues that travel in the bloodstream to cause an effect on other tissues
What is cortisol?
A steroid hormone that is released from the adrenal gland
What are the actions of cortisol?
Increased protein breakdown in muscle (catabolic)
Increased lipolysis in fat (catabolic)
Increased gluconeogenesis in liver (catabolic)
Resistance to stress
Anti-inflammatory effects
Depression of immune system
What is Cushing’s syndrome?
Chronic excessive exposure to cortisol
What is the external cause of Cushing’s syndrome?
Prescribed glucocorticoids (most common cause)
What are the endogenous causes of Cushing’s syndrome?
Benign pituitary adenoma (tumour)
Excess cortisol produced by adrenal tumour
Non pituitary-adrenal tumours producing ACTH (very rare)
What are the signs and symptoms on Cushing’s syndrome?
Plethoric moon-shaped face
‘Buffalo hump’
Abdominal obesity
Purple striae
Acute weight gain
Hyperglycaemia
Hypertension
What is Addison’s disease?
Chronic adrenal insufficiency
What are the causes of addison’s disease?
Main cause at the time of discovery was a complication of tuberculosis
Most common cause now is destructive atrophy from autoimmune disease - exact reason for autoimmunity is unknown
Rarer causes include fungal infection, adrenal cancer, adrenal haemorrhage
What are the signs and symptoms of Addison’s disease?
Postural hypotension
Lethargy
Weight loss
Anorexia
Increased skin pigmentation
Hypoglycaemia
Where is the thyroid gland?
Lies against and around front larynx and trachea
Below thyroid cartilage
Isthmus extended from 2nd to 3rd rings of the trachea
2 lobes joined by isthmus
‘Bow tie’ shape and location
Parathyroid and thyroid are distinct glands
What are the 2 main hormones produced by the thyroid gland?
T3 - tri-iodothyronine
T4 - thyroxine
T3
Secreted directly from the thyroid gland
Influences body metabolism
T4
Converted into T3 in tissues and cells
Iodine is essential for the formation of T3 and T4
TSH stimulates the release of T3 and T4
What are the functions of T3 and T4?
Essential for normal growth and development, especially of skeletal and nervous system
Most other organs and systems are influenced by thyroid hormones - heart, skeletal muscles, skin, digestive organs, reproductive organs
What is Hypothyroidism?
Underactive thyroid
Not enough thyroxine (T4) is produced for the body’s needs
Most common
What is hyperthyroidism?
Overactive thyroid
Too much thyroxine is produced for the body’s needs
What is a goitre?
Enlargement of the thyroid gland
May accompany either hypo or hyperthyroidism but not necessarily present in either
Develops when the thyroid gland is overstimulated
What are the causes of a goitre?
Failure of thyroid gland
TSH or TRH deficiency
Inadequate dietary supply of iodine
Radioactive iodine
Autoimmunity
Post surgery
Congenital
Anti-thyroid drugs
What are the symptoms associated with a goitre?
Obesity
Lethargy
Intolerance to cold
Bradycardia
Dry skin
Slope is
Hoarse voice
Constipation
Slow reflexes
Low T3 and T4
Elevated TSH
What is Hashimoto’s disease?
Autoimmune disease resulting in destruction of thyroid follicles
Leads to hypothyroidism
Most common disease of the thyroid gland
5 times more common in women than in men
What are the signs of Hashimoto’s disease?
Low T3
Low T4
Elevated TSH
Goitre may or may not be present
What is the treatment for Hashimoto’s disease?
Oral Thyroid hormone
T4 used since longer half life
What are the causes of hyperthyroidism?
Autoimmune Graves’ disease
Toxic multinodular goitre
Solitary toxic adenoma
Excessive T4 or T3 therapy
Drugs - amiodarone
Thyroid carcinoma
What are the symptoms of hyperthyroidism?
Weight loss
Irritability
Heat intolerance
Tachycardia
Fatigue, weakness
Increased bowel movements
Sweating and tremor
Breathlessness
What is graves’ disease?
Autoimmune disease resulting in hyperthyroidism
Caused by production of thyroid stimulating immunoglobulin (TSI)
TSI continuously stimulates thyroid hormone secretion (outside normal negative feedback control)
What are the symptoms of graves’ disease?
Increase in BMR
Excessive sweating
Decrease in body weight
Muscle weakness
Heart palpitations
Bulging eyes
What is melatonin?
Hormone linked to sleep
Darkness stimulates release
Light inhibits secretion
Secreted into blood and enters CSF
Excited in urine
Production decreases with age
What are the implications of melatonin for patients?
Noisy bright wards decrease secretion
May need supplements
Out of sync circadian rhythm - poor quality or life, poor mental health , poor physical health decrease in bowel movements
Links to diabetes
Links to obesity
What are the 5 tissues comprising the MSK system?
Bones
Ligaments (attaching bone to bone)
Cartilage (protective gel like substance lining joints and intervertebral disks)
Skeletal muscles
Tendons (attaching muscles to bone)
What is Catabolism?
The set of metabolic pathways that breaks down molecules into smaller units that are either oxidised to release energy or used in other anabolic reactions
What is anabolism?
The set of metabolic pathways that construct molecules from smaller units, these reactions require energy, known also as an endergonic process
What impact does glucagon have on muscles?
Promotes skeletal muscle wastage to supply amino acids for energy (gluconeogenesis)
What impact does cortisol have on muscles?
Secreted by adrenal glands
Helps to deal with stress
Increases protein breakdown
Decreases protein synthesis
What impact does adrenaline have on muscles?
Stimulate sympathetic nervous system
Breaks down muscle mass by using ATP and fuel stores in preparation for exercise
What impact does testosterone have on muscles?
Increases growth hormone release
What impact does oestrogen have on muscles?
Increases muscle metabolism
Reduced muscle break down
Helps repair muscles
What impact does Insulin-like Growth Factor-1 have on muscles?
Released from liver
Signal to cells to undergo hypertrophy and cell division
What are osteoblasts?
Bone-building cells - they deposit new bone tissue around themselves, they eventually become trapped in tiny pockets in the growing bone, and differentiate into osteocytes
What are osteocytes?
Mature bone cells - they do not divide and are responsible for bone formation and calcium homeostasis
What are osteoclasts?
Bone-reabsorbing cells - breakdown bone releasing calcium and phosphate. As new bone cells are made, old ones are destroyed by osteoclasts
What impact does oestrogen have on bone?
Regulates metabolism
Promotes activity of osteoblasts
Prevents bone cell death by osteoclasts
What is osteoporosis?
When the skeletons loses mineral density, the structure becomes thin and unable to take normal weight, leaving bones that break easily
What are the risk factors for osteoporosis?
Gender
Heredity
Age
Fracture history
Medical conditions
Medications
What conditions can cause bone loss?
Alcoholism
Cancers
Coeliac disease
Crohn’s disease
Cushing’s disease
Diabetes Type 2
Eating disorders
Hyperthyroidism
Hypogonadism
Liver disease
Malabsorption
Rheumatoid arthritis
