Theme 5: Diseases of the endocrine system Flashcards
What is the pineal gland?
a tiny organ above the 3rd ventricle in the brain responsible for the secretion of melatonin
What are the endocrine organs in our body
- pineal gland
- pituitary gland
- parathyroid gland
- thyroid gland
- adrenal gland
- pancreas
- ovary
- testis
What is an endocrine organ?
endocrine organ secretes hormones directly into the blood stream to reach a distant target organ
What is an exocrine organ?
secretes out material directly into the GI tract, respiratory tract or onto the skin surface
What are neurocrine hormones?
secretion of hormones into the bloodstream by neurones
What are endocrine hormones?
secretion of hormones into the bloodstream by endocrine glands
What are paracrine hormones?
hormone molecule secreted by one cell affects adjacent cells
What are autocrine hormones?
hormone molecule secreted by a cell affects the secreting cell
What is said to be the master of the endocrine system?
pituitary gland
Where is the pituitary gland?
in the sella turcica of sphenoid bone
What surrounds the pituitary gland?
posteriorly - mamillary bodies
anteriroly - optic chiasma
How is the pituitary gland divided?
- Anterior lobe
- called the adenohypophysis - Posterior lobe
- called the neurohypophysis
What is the function of the anterior pituitary/adenohypophysis?
-produces and secretes the majority of the pituitary hormones
What is the function of the posterior pituitary/ neurohypophysis?
doesn’t produce any hormones, but it releases two hormones that are produced in the thalamus - oxytocin and ADH
What hormones are produced by the anterior lobe?
TSH, ACTh, FSH and LH, GH, PRL, endorphins
What is the most common type of pituitary tumour?
they are almost always benign adenomas
What might be some local effects of a pituitary tumour?
pressure on the optic chiasm (bitemporal hemianopia = ‘tunnel vision’)
or adjacent pituitary cells
How does a prolactinoma form?
a mutation in the lactotroph cells in the anterior pituitary - results in excess prolactin production
What are the symptoms of a prolactinoma?
- galactorrea - increased secretion from breasts
- gynecomastia - enlarged breast tissue in men
- amenorrhea
- infertility
If the anterior pituitary adenoma is a result of the cells responsible for producing growth hormone, what might be the symptoms?
gigantism and acromegaly (enlarged limbs, hands and feet)
acromegaly is excess GH after growth plates have closed
What is the best clinical test for confirmation of acromegaly?
oral glucose suppression test
What is gigantism
abnormally high linear growth due to the excessive action of IGF-1 before the closure of the epiphyseal growth plates in childhood
Which 3 hormones does the thyroid gland secrete?
T3
T4
Calcitonin
Explain how the hypothalamic-pituitary-thyroid axis works
- Thyroid gland produces T3 and T4 which has a negative feedback effect back to the pituitary and hypothalamus, both of which have stimulatory effects
- SO when the levels of T3 and T4 are increased, this tells the hypothalamus to produce less TRH and less TSH
What is hypothyroidism?
- due to insufficiency of circulating T3 and T4 hormones
- results in overall reduction in the basal metabolic rate and reduction in production of T3 and T4
- more common in women
- peak age 59 years
- increased risk of carcinoma
What is the commonest cause of hypothyroidism?
hashimoto’s thyroiditis
if a patients case of hypothyroidism is congenital, what main symptom will they have?
cretinism - physical growth deformity and mental impairment
Other than hashimotos thyroiditis, what are some other causes of hypothyroidism?
iodine deficiencies, drugs, post surgery and post radioiodine therapy
What are the signs and symptoms of hashimoto’s?
Signs:
- hypothermia
- bradycardia
- periorbital edema
- hair loss
Symptoms:
- fatigue
- weak ness
- weight gain
- constipation
- cold intolerance
- dry skin
- hoarse voice
- depression
What is hyperthyroidism?
- syndromes due to excess T3 and T4
- increased basal metabolic rate (bmr)
What is the commenest cause of hyperthyroidism?
Grave’s disease
IgG auto-antibody that binds to the thyroid epithelial cells to produce more TSH
peaks in 30s/40s
What are the signs and symptoms of Grave’s disease?
Signs: pretibial myoedema hair loss wide-eyed stare proptosis tachycardia hyperactive reflexes
What is the 2nd most common cause of hyperthyroidism?
- multinodular goitre (MNG)
- enlargement of thyroid with varying degrees of nodularity
What does euthyroid mean?
no symptoms of hyperthyroidism
Name a common cause of a solitary thyroid nodule (other than MNG)?
thyroid follicular adenoma
- solid mass with fibrous capsule
- sometimes functional (producing excess thyroxine) but usually isnt
- F>M
Name 3 types of thyroid tumours
- Thyroid follicular adenoma
- Thyroid follicular carcinoma
- well differentiated malignant tumour with good prognosis
- presents with solitary nodule in thyroid gland
- invades blood vessels - Papillary thyroid carcinoma
- well differentiated malignant tumour with good prognosis
- most common thyroid carcinoma
- younger, F>M
- invades lymphatics
Where are the parathyroid glands and how many do we have?
- located in the posterior aspect of the thyroid
- 90% have 4 glands. rest have 3 or 5
What are the functions of the parathyroid gland?
Calcium homeostasis:
- produces parathyroid hormone (PTH) which stimulates calcium release from bones
- calcitonin - reduces calcium levels in the blood
What are the secondary causes of hyperparathyrodism? in response to hypocalcemia?
- renal failure
- decreased calcium e.g low oral intake, malabsorption, VitD
- inhibition of bone resorption
What are the signs and symptoms of primary hyperparathyroidism?
renal stones muscle weakess tiredness thirst and polyuria anorexia constipation all a result of electrolye imbalances e.g hypercalcaemia
How is the adrenal gland divided into two?
outer cortex
inner medulla
What are the zones of the outer cortex?
Zona glomerulosa
Zona fasciculata
Zona reticularis
What does the zona glomerulosa secrete?
“salt”
mineralocorticoids e.g aldosterone
What does the zona fasciculata secrete?
“sugar”
glucocorticoids e.g cortisol
What does the zona reticularis secrete?
“sex”
androgens
What do chromaffin cells in the medulla secrete?
“stress”
catecholamines e.g norepi, epi
What is Cushing’s syndrome?
- result of adrenal gland
- rare endocrine disorder due to excessive cortisol
- between ages 25-40
What are some endogenous causes of cushings?
- adrenal cortical tumours
- adrenal cortical hyperplasia
- ACTH secreting pituitary adenoma
When is paraneoplastic cushings seen?
small cell lung carcinoma
What is the exogenous cause of cushings?
patients on steroids
What are the signs and symptoms of cushings
- upper body obesity with thin arms and legs
- red, round face
- high blood sugar
- high BP
- vertigo
- blurry vision
- acne
- purple striae
- menstrual irregularities
- hirsuitism
- severe depression
- cognitive difficulties
- emotional instability
- sleep disorders
- fatigue
Which organ secretes aldosterone?
adrenal gland
What is Conn’s syndrome?
- hyperaldosteronism
- can be primary or secondary
- increase release of aldosterone from zona glomerulosa
- 30-50 years, W>M
What are the signs and symptoms of Conn’s syndrome
high BP, headache, muscular weakness, muscle spasms, excessive urination and cardiac arrythmias
What is Waterhouse-friderich syndrome?
- acute adrenal insufficiency
- generally secondary to septicaemia
- adrenal gland failure (stops producing hormones) due to bleeding in adrenal glands
What is Addison’s disease?
- primary chronic adrenal cortical insufficiency
- secondary due to failure of ACTH secretion
- autoimmune form is most common
- lack of mineralocorticoids and glucocorticoids
- treatment with long term steroid replacement
What is the triad of Addison’s disease?
- hyperpigmentation
- postural hypotension
- hyponatraemia
- GI disturbances
What are the signs of an acute adrenal crisis?
- fever
- syncope
- convulsions
- hypoglycaemia
- severe vomiting and diarrhea
What is a pheochromocytoma?
- catecholamine-secreting tumours of the adrenal medulla
- produces adrenaline, noradrenaline
- mostly sporadic but familial syndromes are von hippel-lindau disease etc
- excellent prognosis when benign
- malignant tumours may require aggressive treatment
What are the symptoms of pheochromocytoma?
racing heart beat headaches pallor sweating high BP
What would we immediately treat thyrotoxicosis with and why?
- Beta blockers - to control the symptoms of hyperthyroidism e.g tachycardia and sweating
- Carbimazole - blocks production of thyroid hormone
In primary hypothyroidism, why do we see a high TSH?
due to reduced negative feedback on the pituitary so it produces more TSH in attempt to stimulate the pituitary to secrete more T4
What are the 2 first line screening tests for cushings?
24hr urine cortisol and overnight dex test
