Lecture: Endocrine Flashcards
What does the endocrine system include
Endocrine glands and their hormones
Function of endocrine system
Secrete hormones into the bloodstream
What is a hormone
Chemical messenger which targets a specific group of cells, in order to cause that group of cells to do some activity or stop doing an activity
What are exocrine glands
Glands that release their secretions into ducts or tubes
E.g liver releases bile into the gall bladder
Pancreas releases pancreatic juice into small intestine
Hormones that are proteins
Growth hormone
Glycoprotein hormone s(e.g. luteinising hormone)
Hormone that is a polypeptide
Insulin
Peptide hormone example
Thyrotropin-releasing hormone
Hormones that are amino acid derivatives
Dopamine, catecholamine, thyroid hormone
Examples of steroid hormones
Mineralocorticoids
Glucocorticoids
Sex steroids
Example of sterol hormones
Vitamin D
What are binding proteins
Proteins that bind to hormones and carry them around the circulation
Binding proteins for T4, T3
Thyroxine binding globulin (TBG)
Thyroxine binding prealbumin (TBPA)
Albumin
Binding proteins for testosterone
Sex hormone binding globulin
Albumin
Binding protein for cortisol
cortisol binding globulin
Binding protein for GH
GH-binding protein
Binding protein for IGF-1
IGF-binding protein-3 plus the acid labile subunit (ALS)
Function of hormones
Differentiation of reproductive and CNS in foetus
Stimulation of growth and development
Coordination of the male and female reproductive system
Maintenance of internal environment
Adaptation to emergency demands of the body
How are hormones regulated
By negative/positive feedback mechanisms
Example of negative feedback mechanism
Secretion of insulin which tells cells to take in glucose
Glucose levels drop, secretion of insulin stops
Example of positive feedback mechanisms
Release of oxytocin to release milk from baby suckling
Name human endocrine glands
Pituitary Thyroid Parathyroid Adrenal Pancreas Testes & ovaries
Function of parathyroid
Control metabolism of calcium
What does under secretion of parathyroid hormone result in
Never disorders
Brittle bones
Clotting problems
What hormones are released from adrenal glands
Cortisone and adrenaline
Function of cortisone
Regulate carbohydrate, protein and fat metabolism
Function of adrenaline
Raise blood sugar levels and increases heartbeat and breathing rates
What does under secretion of adrenaline result in
Inability to deal with stress
What is the pituitary
Gland is a round organ located behind the bridge of the nose at the base of the body
How many hormones does the pituitary secrete
9
What regulates pituitary function
Hypothalamus
Hypothalamic-pituitary-axis
What can hyperprolactinaemia cause
Infertility
What are causes of hyperprolactinaemia
Stress
Drugs
Hypothyroidism
How to differentiate between prolactinoma and idiopathic hypersection
Detailed radiology + dynamic tests of prolactin secretion
[Serum prolactin rises after administration of TRH observed in idiopathic hyperprolactinaemia but not tumour)
Name two hormones secreted by posterior pituitary
antidiuretic hormone
oxytocin
(synthesised in the hypothalamus)
How are anterior pituitary function tests preformed
TRH, GnRH and insulin are administered and measured at 0, 30 and 60 m
Causes of hypopituitarism
Tumour Infarction Traume Congenital malformation Infection Hypothalamic disorder
What is a cause of goiter
Iodine deficiency in diet
Normal T4 plasma concentration
100 nmol/L
How is T3 produced
Liver and kidneys (peripheral tissues) deiodinate T4 to produce 2/3rds of T3 (Conc of 2 nmol/L)
What does the biosynthesising of thyroid hormones involve
Trapping of circulating iodide by thyroid gland
incorporation of iodine into tyrosine
Coupling of iodinated tyrosyl residues from the thyronines within the protein backbone of the Tg protein in the follicular lumen. Endocytosis followed by proteolytic cleavage of Tg releases the iodothyronines into circulation
T4 can be metabolised to
reverse T3 which is biologically inactive
What proteins transfer T4 & T3
TBG (70%)
Alb (25%)
Transthyretin (5%)
When do highest level of TSH occur
between 0200 and 0400
(lowest at 1700 to 1800
Causes of hypothyroidism
Primary hypothyroidism
Idiopathic hypothyroidism, hashimotos thyroiditis, surgical removal of thyroid
Symptoms of hypothyroidism
Weakness, skin changes (dry), lethargy, slow speach, eyelid edema, cold, decreased sweating, thick tongue, forgetfulness
What confirms diagnosis of graves disease
Raised T4, suppressed TSH + TSH receptor antibody level
Hyperthyroidism causes
Graves disease
Toxic multi nodular goitre
Thyroiditis
Excessive T4 & T3 ingestion
Hyperthyroidism clinical features
weight loss sweating heat intolerance fatigue angina/heart failure diarrhoea
