Flashcards in Endocrinology Deck (41)
How does the posterior pituitary differ from the anterior pituitary?
Hypothalamus secretes hormones which travel down axons to the posterior pituitary - direct neural link
Anterior pituitary - the hypothalamus secretes hormones which trigger the secretion of other hormones from the anterior pituitary
Name two conditions associated with hypersecretion of hormones
Congenital adrenal hyperplasia
Name two conditions associated with hyposecretion of hormones
Describe the events, triggered by stress, that take place in the HPA axis
The hypothalamus secretes CRH in response to stress. This then triggers the release of ACTH from the anterior pituitary. This then leads to the release of cortisol from the adrenal cortex.
Negative feedback loop induced by cortisol to stop the hypothalamus producing CRH and the anterior pituitary releasing ACTH
Which three protein hormones are released by the placenta?
What hormone is produced by the heart to reduce blood volume?
If someone is hypertensive, atrial natriuretic peptide - stimulates kidneys to excrete more salt, thereby decreasing blood volume and therefore blood pressure
Where are the parvicellular neurones located and what do they do?
Located in the hypothalamus and secrete regulatory hormones into the blood stream, which travel through the portal system to the anterior pituitary, triggering secretion of other hormones
Where are magnocellular neurones located and what do they do?
Located in the hypothalamus and have long axons which extend down into the posterior pituitary. When hypothalamus receives a signal, hormones are released from the pituitary
What is the difference between tropic and non-tropic hormones?
Tropic regulate the function of other primary endocrine glands to produce effector hormones. Non-tropic hormones act directly on other tissues
Name the tropic hormones
Name the non-tropic hormones
Hypersecretion of which hormone leads to gigantism in children?
Hypersecretion of growth hormones leads to which condition in adults?
What is the difference between somatostatin and somatotropin?
Somatostatin (GHIH) regulates the secretion of growth hormone. Used to treat GH hypersecretion
Somatotropin is used as treatment for growth hormone deficiency
How is acromegaly treated?
What are the causes of GH deficiency?
Insufficient hormone production caused by:
- mutation of GH gene
- head injury of infection
- hypothalamic or pituitary tumour
GH resistance caused by:
- GH binding protein mutations
- GH receptor mutations
What are the functions of oxytocin?
Stimulation of milk ejection
Stimulation of uterine contractions at birth
Describe the positive feedback loop, linked to oxytocin, that takes place during labour
Pressure on the cervix applied by baby activates sensory neurones
Hypothalamus secretes oxytocin in waves
Oxytocin diffuses down to the uterus, receptors in the uterus respond and the uterus contracts
This pushes the baby's head further down onto the cervix, applying more pressure so more oxytocin is released --> gradual build up of contractions
What is diabetes insipidus and what are the types?
Excessive urine production - up to 16L/day. Causes:
- 1) Hypothalamic diabetes insipidus
-2) Nephrogenic diabetes insipidus
What is the difference between hypothalamic diabetes insipidus and nephrogenic diabetes insipidus?
Hypothalamic is due to decreased ADH secretion, caused by head trauma, infection etc.
Nephrogenic is due to improper response of the kidneys to ADH, meaning they cannot concentrate urine. Caused by renal disease.
How is diabetes insipidus treated?
Hypothalamic - exogenous vasopressin
Nephrogenic - increase water consumption
Where is melatonin produced and what is its function?
Melatonin is produced in the pineal gland by pinealocytes. It plays a role in regulating circadian rhythm.
Production is inhibited by light to the retina and is permitted by darkness
What can melatonin be used to treat?
Seasonal affective disorder and insomnia
What is the rate limiting step in steroidogenisis?
Conversion of cholesterol to pregnenolone
What is the main carrier protein for exogenous steroids?
What is the carrier protein for natural and synthetic steroids?
How is addison's disease treated?
Hydrocortisone with or without fludricortisone
How is congenital adrenal hyperplasia treated?
Synthetic steroid e.g. betamethasone
What is the role of aminoglutethimide?
Blocks steroid synthesis, used in treatment of Cushing's syndrome, prostate cancer