Endocrinology Flashcards
Where is the pituitary gland located
sella turcica of the sphenoid bone, attached to the hypothalamus
What hormones are secreted from the anterior pituitary
o Growth Hormone o Prolactin o FSH o LH o TSH o ACTH
What is the difference of the hypothalamic involvement between hormones secreted from the anterior and posterior pituitary
ANT: these hormones are regulated by hormones from the hypothalamus
POS: these are synthesised in the hypothalamus - pass into the posterior pituitary to be secreted
What hormones are secreted from the posterior pituitary
o Oxytocin
o ADH
What is the most common disease of the anterior pituitary
Pituitary adenoma
What type of tissue is most commonly affected with a pituitary adenoma
Glandular tissue
What are the most common causes of pituitary adenoma
Most cases are sporadic, but they can occur as part of the MEN1 syndrome
What are the 2 main types of pituitary adenoma and how do they present
o Functional adenomas = Effects related to excess hormone secretion (very small at presentation - because the symptoms mean they are picked up earlier)
o Non-functional adenomas = don’t produce hormones - larger and therefore present with mass effects (however many are not detected - as they remain small)
” Mass effects
o Bitemporal hemianopia - due to compression of the optic chiasm, thereby affecting the optic nerves
o Diplopia - compression of CN III, IV, VI
o Non-specific symptoms of a intracranial mass ie headache
What is a prolactinoma
Pituitary adenomas that produce excess prolactin
They are the most common type of functional adenoma
How would a prolactinoma present in a woman of reproductive age
Oligomenorrhoea - infrequent/light menstruation (4-9 periods a year)
OR
Galactorrhoea - spontaneous flow of milk from the breast unassociated with pregnancy or breast feeding
(Note these patients generally have small tumours and present early)
How would a prolactinoma present in a man/post-menopausal woman
” Mass effects - headache / visual disturbance
OR
“ Galactorrhoea (occasionally)
These patients generally have larger tumours on presentation.
How do ACTH secreting adenomas present
Cushing’s syndrome
How do GH secreting tumours present
Acromegaly
List symptoms of acromegaly
" Facial changes o Protruding supraorbirtal ridges o Enlarged nose o Coarse facial features o Prognathia " Headaches " Thickened calvaria " LV hypertrophy " HTN " Insulin resistance " Hepatomegaly " Impotence and loss of libido / amenorrhoea in women " Large hands " Thickened skin " Hyperostosis " Degenerative joint disease " Peripheral neuropathy (nerve compression) " Large feet and heel pad
Mortality is doubled in patients with acromegaly- why
Mainly due to high incidence of CVD due to LV hypertrophy and HTN.
Also has another risk factor for CVD as it is a diabetogenic state (insulin resistance)
How do TSH secreting adenomas present
Thyrotoxicosis
not a very common cause of thyrotoxicosis though!
What are common causes of thyrotoxicosis
" Graves (80%) " Toxic multinodular goitre - secretes thyroid hormone independently of TSH " A functional thyroid adenoma " Drugs - amiodarone " Thyroiditis (certain types)
Where are the adrenal glands located
located in the retroperitoneum, superior to the kidneys
What are the functional divisions of the adrenal glands
Cortex and medulla
How is the adrenal cortex divided
o Zona glomerulosa = mineralocorticoids (ALDOSTERONE)
o Zona fasiculata = glucocorticoids (CORTISOL)
o Zona reticularis = ANDROGENS
What does the medulla of the adrenal gland secrete
catecholamines - eg. adrenaline + noradrenaline
How does the HPA axis regulate cortisol
- Hypothalamus secretes CORTICOTROPHIN RELEASING HORMONE - CRH
- Stimulates the anterior pituitary to secrete ACTH
- ACTH acts on the adrenal gland to stimulate the release of cortisol
- Cortisol has a negative feedback effect on both the hypothalamus and anterior pituitary - supressing CRH and ACTH
What is Cushing’s syndrome
A metabolic disorder due to persistent excess circulating glucocorticoids
List symptoms of Cushing’s syndrome
- Weight gain - pattern of fat deposition = marked trunkal obesity and a moon face
- Muscle weakness - proximal myopathy.
- Gonadal dysfunction = menstrual irregularities in women and loss of libido in men
- Hirsuitism in women
- HTN - secondary
What is the most common cause of Cushing’s syndrome
Exogenous administration of glucocorticoids
List the main causes of Cushing’s syndrome
- Exogenous administration of glucocorticoids
- Pituitary adenoma which secretes ACTH
- An adrenal cortical adenoma which secretes cortisol
- Paraneoplastic syndrome
A patient with cushing’s syndrome has adrenals that have atrophied. What is the most likely cause behind their symptoms?
Exogenous administration of glucocorticoids
A patient with cushing’s syndrome has adrenals that have undergone hyperplasia. What is the most likely cause behind their symptoms?
Pituitary adenoma secreting ACTH
What is Cushing’s disease
Pituitary adenoma which secretes ACTH
A patient with Cushing’s syndrome is found to have an adrenal cortical adenoma. Which cells will this have arisen from? (not specific, just wants the location)
Cells in the zona fasciculata
What is the equation for BP
BP= CO x TPR
What are the 2 main factors affecting BP
Vasoconstriction - TPR
Increase in Na+ retention (+ H2O = + circulating volume = + CO)
What is the equation for CO
CO= HR x SV
What is the most common cause of primary hyperaldosteronism?
Conn’s syndrome (aldosterone producing adrenal cortical adenoma)
What is the second most common cause of primary hyperaldosteronism
Bilateral adrenal cortical hyperplasia
Briefly explain RAAS
- If BP falls there is reduced blood flow to the renal artery
- This hypoperfusion stimulates release of renin
- Results in the production of Ang II. Its effects include:
a. Stimulates release of aldosterone from the adrenal cortex. Aldosterone increases Na+ (and water) reabsorption by the kidney tubules - increases blood volume and raises BP
b. Vasoconstriction of arterioles (systemic) = raises BP
c. Stimulates release of ADH by posterior pituitary - stimulates water reabsorption - increases blood volume = raises BP - Restoration of blood flow = less renin released and so downregulates renin
What are the effects of Ang II
a. Stimulates release of aldosterone from the adrenal cortex. Aldosterone increases Na+ (and water) reabsorption by the kidney tubules - increases blood volume and raises BP
b. Vasoconstriction of arterioles (systemic) = raises BP
c. Stimulates release of ADH by posterior pituitary - stimulates water reabsorption - increases blood volume = raises BP
What are the main effects of hyperaldosteronism
- Excess Na+ reabsorption = hypernatreamia
- Excess K+ loss into urine = hypokalaemia
- Excess Na+ retention = excess H2O reabsorption = + circulatory volume = + CO = + BP
What is a phaeochromocytoma
Neuroendocrine tumour of the adrenal medulla, which secretes catecholamines
What is the main effect of a phaeochromocytoma
Hypertension
How do phaeochromocytomas present
Usually asymptomatic - may complain of episodes of throbbing headache/sweating/palpitation (due to episodic increases in circulating catecholamines).
How do you investigate a suspected phaeochromocytoma
24h urine collection for catecholamine and metanephrine measurement
