Endocrinology Flashcards
Define Endocrinology
The study of endocrine glands (epithelial tissues) and the substances they secrete (hormones)
Define Endocrine and Exocrine glands
Secretes hormones into the bloodstream (chemical substance that has specific effect on target cells)
Secrete products through ducts onto an epithelium
Define Paracrine and Autocrine signalling
Paracrine = signals released that act close to the target cell
Autocrine = signals released from and target, the same cell
What are the main endocrine organs?
Heart Gut Liver Adipocytes Placenta Testes/Ovaries Kidney Adrenal glands Pancreas Thyroid Pituitary gland
What are the main endocrine hormones - their function and targets?
Insulin - secreted by B-cells to reduce high blood glucose levels
Glucagon - secreted by a-cells to increase blood glucose levels
Thyroid hormones TSH, TRH - regulate basal metabolic rate on tissues
Gastric hormones (Somatostatin, Gastrin, Histamine) Enteric hormones (VIP, GIP, CCK, Secretin, Motilin) RAAS - ADH
What are the 3 major molecular types of hormones?
Polypeptides
Modified amino acids (single amino acids, dipeptides, small peptides)
Steroids (from Cholesterol)
- derived from amino acids or lipid precursors
Where are prostaglandins derived from?
Where are steroids derived from? Name 3 examples
Prostaglandins from fatty acids
Cortisol, sex steroids and vitamin D are examples of steroid hormones, derived from cholesterol
Both are lipid precursors
Name some hormones derived from amino acids:
Catecholamines, serotonin (single amino acids)
Thyroid hormones (dipeptides)
TRH, vasopressin, somatostatin (small peptides)
Insulin, PTH (intermediate size peptides)
Gonadotrophs (FSH, TSH, LH) are complex polypeptides
What’re the differences between peptides & catecholamines and steroids & thyroid hormones?
Peptides & Catecholamines: rapid in action, short half life, bind to cell membrane receptors to have rapid effect by activating primed enzymes and secretory vesicles
Steroids & Thyroid hormones: long plasma half life, slow speed of effect (hours-days), bind intracellularly to stimulate protein synthesis
How are water soluble and fat soluble hormones transported in the blood?
Water soluble hormones dissolve in plasma; large and hydrophilic so bind to cell surface receptors (GPCRs/RTKs) to pass cell membrane
Fat soluble hormones: travel in blood bound to plasma proteins (inactive) then dissociate to get into cell via protein carrier and bind to cystoplasmic receptor to activate transcription factor in nucleus (eg steroid hormones)
What’re tropic and trophic hormones?
Tropic = hormone that effects other endocrine glands
Trophic = affects growth directly
Where would you see positive feedback mechanism with regards to endocrinology?
Luteinising hormone surge in ovulation (increased levels of effector hormone further increase secretion of tropic hormone)
Outline negative feedback in endocrine systems
Gland receives signal from another gland (via tropic hormone) to increase or inhibit secretion
Gland secretes effector hormone to have effect on target cells and inhibit further secretion of the tropic hormone
What’s the difference between primary and secondary endocrine dysfunction?
Primary: too much effector hormone from endocrine organ
Secondary: overstimulation of effector endocrine gland by excess tropic hormone
Cushing’s syndrome is an effect of excess of what hormone?
Glucocorticoid excess
Symptoms: central weight gain and ‘moon face’, thin skin, depression, polyuria
Treatments: surgery to remove tumour or drugs to reduce cortisol production
