Week 9 - Hormones And Chromosomes Flashcards
What are hormones and what are the three types?
Hormones are signalling molecules They can be) 1) peptides 2) amino acid derivatives 3) lipid derivatives
How do lipid derived hormones act when they arrive at a cell?
As they are lipid soluble, they diffuse through the plasma membrane and bind to their intracellular receptors
What are the two types of lipid derived hormones?
D - steroid hormones (cholesterol derivatives, small molecules bound to plasma proteins in the blood) - eicosinoids (arachidonic acid derivatives)
What are the two hormones secreted by the posterior pituitary gland?
Anti-diuretic hormone (ADH) and Oxytocin
What is the effect of ADH?
At the kidneys; Increases permeability to water at distal and collecting tubules At the arterioles; Causes vasoconstriction
What are the effects of oxytocin?
At the uterus; 1) stimulates uterine contractions At the breasts; 2) stimulates milk ejection
What are the features of the posterior pituitary gland
1) Pars nervosa - nerve fibres originate at hypothalamus, transport hormones to posterior pituitary 2) DIRECTLY connected to hypothalamus 3) neural lobe or neurohypophysis 4) DOESN’T synthesise hormones, hormones are synthesised by HYPOTHALAMUS neurones.. And secreted by the posterior pituitary
You are on holiday in South Africa and the sun is scorching. You start to get dehydrated. Outline the mechanism that regulates blood osmolarity in terms of hormonal control.
An increase in osmolarity is detected by osmoreceptors in hypothalamus Hypothalamus produces ADH, which is transported to the posterior pituitary gland by nerve fibres ADH secreted from posterior pituitary gland increases H2O permeability thus water is reabsorbed at distal and collecting tubules Osmolarity decreases
What re the features of the anterior pituitary gland?
1) porta distalis - portal blood vessels that connect pituitary and hypothalamic capillary beds together 2) synthesises its own hormones, 7 hormones released from 5 cell regions
What is the distribution of Somatotrophs in the anterior pituitary gland? What does this cell region secrete?
50% of pituicytes in anterior pituitary gland Somatotrophs secrete growth hormone
What are the the 7 hormones of the anterior pituitary gland and where do they target?
See week 9 Hormones
What controls hormone secretion from the anterior pituitary?
Hormones from the hypothalamus; They can be stimulatory or inhibitory hormones STIMULATORY (their functions are pretty obvious from the name!) - growth hormone releasing hormone - gonadotropin releasing hormone - corticotropin releasing hormone - thyrotopin releasing hormone INHIBITORY - dopamine (prolactin inhibiting hormone) - somatostatin (inhibit growth hormone secretion)
What factors effect growth as well as growth hormone?
- nutrition - presence of sex hormones (secondary characteristics - if have chronic illness - genetic determination
What are the most abundant types of hormones? Give an example of this type?
Polypeptide hormones. E.g. CCK
What areas if the body does growth hormone affect?
MUSCLES - * decrease in glucose intake * increase in amino acid intake - increased muscle mass Protects against hyperglycaemia ADIPOSE TISSUE - * decrease in glucose uptake * increase in lypolysis * Decrease in fatty deposits LIVER - * increase in gluconeogenesis * decrease in glucose intake * increase in protein synthesis * …. Leads to synthesis if IGF1 and IGF2
What does the synthesis of IGF1 and IG2 lead to?
Soft tissue growth - increase in protein synthesis - increase in chondrocyte proliferation Skeletal growth - increases cartilage formation - increases bone depOsition
How is growth hormone regulated?
Growth hormone releasing hormone and growth hormone inhibiting hormone (somatostatin)
What stimuli to the hypothalamus influence the secretion of growth hormone?
Metabolic - Hypoglycaemia Low fatty acids Neural - Stress, exercise, sleep Hormonal- Sex steroids Conditions such as starvation and anorexia
What are the clinical features if growth hormone excess in patients who had excess pre teen?
Growth hormone excess before epiphyseal plate fusion; GIGANTISM - increased skeletal and soft tissue growth -
What are the clinical features of growth hormone excess in adults? What is the cause of this excess?
Epiphyseal plate has closed. ACROMEGALY - cardiomegaly - course facial features - large teeth, nose, hands - diabetic - protruding jaw
A 17 year old patient comes to see you in your GP practice with her parents. Their parents are worried because their daughter’s features have changed, which they describe as “enlarged and more prominent”. they show you a picture of when she was younger. You notice her hands Re more enlarged and she has a prominent jaw. The patient mentions she’s started to urinate more frequently. What do you think should be investigated and what treatments are you considering if any?
Consider patient’s age, she is 17 and her epiphyseal plates have not fused. Patient most likely has acromegaly possibly caused by a pituitary tumour. MRI scan to see if there is a pituitary tumour. Treatment options: - surgical removal of tumour - if surg. Unsuccessful) somatostatin receptor agonist (to inhibit further somatostatin) - growth hormone receptor antagonist
What are the clinical features of pituitary dwarfism and does this occur in children or adults?
In CHILDREN! No symptoms of Growth hormone insufficiency in adults Excess subcutaneous fat Normal body proportions Slow growth rate
What hormones do the adrenal glands secrete?
Adrenal medulla secrete catecholamines Adrenal cortex secretes steroid hormones
The adrenal glands each are basically 2 endocrine glands with hormones being secreted from the cortex and the medulla. What hormones are secreted from where, mention the zones of the adrenal cortex as well.
To remember the zones : GUIDE ALAN FOWARD CAUSE REEM IS ANGRY From top to bottom (Capsule) Zona Glomerulosa - Aldosterone (mineral balance) Zona fasiculata - Cortisol (glucose and lipid metabolism) Zona reticularis - Androgen (male sex hormones) (Adrenal medulla) - adrenaline (80%) and noradrenaline (20%)
Name three androgens associated with male development?
1) Testosterone 2) Dihydrotestosterone - Embryo life: causes differentiation of penis in embryo life In later life: male balding, prostate growth, sebaceous gland activity 3) Androstenedione -
Name some testosterone orecursors and where are they converted to tstosterone?
DHEA and DHEa-S which bind less efficiently to androgen receptors (weak steroids) Activated in peripheral tissues They are controlled by ACTH in the anterior pituitary
What is the role of adrenal gland derived testosterone in men?
Is insignificant as role not understood; - secondary characteristics - aggression in boys No consequences in excess or in small amounts
What are the roles of testosterone in women?
Unlike in men, adrenal glands are the primary source of testosterone Responsible for; - growth of pubic and auxiliary hair - sex drive - kick start puberty - maintain muscle and bone mass
What is the cause of adrenal cortex hyperfunction and what are some clinical features?
Over production of ACTH in anterior pituitary gland Hirsutism - when females develop a male pattern of body hair Acne, Irregular periods Breast shrinkage ******* HAIB *******
Hannah comes into your GP asking you for some treatment for her irregular periods and unusual man pattern like hair. What treatment would you give her and why?
Hannah seems to be having over stimulation of ACTH producing more androgens than usual. Treatment would be an anti- androgen such as cyproterone acetate, and ethinylestradiol
What are the clinical features if Addison’s disease?
Destruction of the entire adrenal cortex Low sex hormone Loss of body and pubes hair Loss of libido Muscle wasting and thin limbs Low cortisol Hypoglycaemia Hypercalaemia Hypoaldosteronism
Once LH and FSH enter interstitial space within testes, what are their functions at their targets?
LH - stimulate leydig cells to secrete testosterone
FSH-
stimulate sertoli cells
What is the function of sertoli cells?
Sertoli cells
Can Nourish Cheeky Sperm
Create seminiferous tubules
Nourish germ cells to promote spermatogenesis (note. dont nourish sperm)
Convert testosterone to DHT or oestradiol
Secrete Inhibin which negatively feeds back on FSH
Function of androgen-binding protein?
Binds to an androgen funnily enough! Binds to testosterone - stimulating spermatogenesis
What are the functions of testosterone?
What is Klinefelter syndrome and is it common?
1) COMMON genetic condition where males have an extra X chromosome
2) LOW PRODUCTION OF TESTOSTERONE, undiagnosed until adulthood usually
3) Little or no sperm production
What enzyme converts testosterone to DHT?
5 alpha reductase
What what is an associated disorder, what are the consequences?
5 alpha reductase deficiency
As no DHT is produced you get decreased development of male reporiductive system (see notes on DHT functions)
What is androgen insensitivity syndrome and what are the signs?
1) Body is insentitive to testosterone and DHT.
2) Genetals develop in a female like pattern and testes remain inside the body
3) Persons are genetically male, but genitals are female
