Endocrinology Flashcards
What is goitre?
Any swelling of the thyroid gland
Name 4 possible causes of diffuse smooth goitre.
Physiological (increased demands for thyroid hormone, e.g. pregnancy)
Grave’s disease
Thyroiditis
Dietary iodine deficiency
What general findings would you find in hyperthyroidism?
Warm, moist skin Fine hair/alopecia Peripheral oedema Onchylosis Thyroid acropachy
What two drugs can cause hyperthyroidism?
Iodine
Amiodarone
In what thyroid condition would you see gynaecomastia?
Hyperthyroidism
What is hyperthyroidism?
Condition caused by increased levels of circulating thyroxine (T4) and/or tri-iodothyronine (T3)
In which gender is thyroid disease more common?
Female
How would you investigate hyperthyroidism?
TSH Free T3 and T4 FBC Liver enzymes ESR
What drugs would be used to treat hyperthyroidism?
Beta-blockers for symptom control
Carbimazole or propylthiouracil +/- additional T4 (block and replace method)
What surgery would you consider to treat hyperthyroidism?
Thyroidectomy
Why are hyperthyroid patients encouraged to stop smoking?
Smoking is main risk factor for thyroid eye disease
What is Grave’s disease?
An autoimmune disorder of the thyroid gland
What drugs can cause hypothyroidism?
Lithium
Amiodarone
What is the difference between T4 and T3?
T4 is the pro hormone and is converted to T3 in peripheral tissues, where T3 then has an action
What is TRH and where is it secreted?
Thyrotropin-releasing hormone
Secreted by hypothalamus
What is TSH and what produces it?
Thyroid-stimulating hormone
Produced by thyrotrophs of pituitary gland
What does TSH do?
Increases serum levels of T3 and T4
Promotes conversion of T4 to T3
What are the effects of thyroid hormones of CVS?
Increased heart rate
Increased cardiac output
What are the effects of thyroid hormones on skeletal system?
Increased bone turnover and resorption
In general, what do thyroid hormones do to the body?
Increase basal metabolic rate
Increase rate of oxygen consumption under basal conditions
What produces calcitonin?
Parafollicular (or C) cells in thyroid gland
What is the effect of calcitonin?
Decrease the level of calcium in the blood by inhibiting action of osteoclasts
What is hypothyroidism?
Underactivity of the thyroid gland
Where is the common cause of hypothyroidism?
Primary (from the thyroid gland)
not higher up the axis, i.e. secondary
Name symptoms of hypothyroidism.
Tiredness/malaise Weight gain Cold intolerance Goitre Bradycardia Slow-relaxing reflexes
How would you investigate hypothyroidism?
Serum TSH
Free T3 and T4
FBC
Lipids
What would you expect to see on a blood test of someone with primary hypothyroidism?
High TSH
Low T4
How would you treat hypothyroidism and for how long?
Levothyroxine (synthetic thyroxine)
For life
What is the most common cause of hyperthyroidism?
Grave’s disease
What are the four categories of hormones?
Peptide and proteins
Amino acid derivatives
Steroids
Fatty acid derivatives (eicosanoids)
By which process are protein preprohormones modified in the ER?
Glycosylation
What are steroid hormones derived from?
Cholesterol
Where are steroid hormones synthesised?
Adrenals
Gonads
Placenta
Name the hormones produced and secreted by the anterior pituitary.
LH and FSH Growth hormone Prolactin TSH ACTH
What does the posterior pituitary gland do?
Stores (but does not produce) vasopressin (ADH) and oxytocin
What is the most common cause of pituitary disease?
Pituitary tumour
What is Cushing’s syndrome?
Describes the signs and symptoms associated with prolonged exposure to inappropriately high levels of cortisol
What is Cushing’s disease?
Increase secretion of ACTH from the anterior pituitary
What is the most common cause of Cushing’s disease?
Pituitary adenoma
How would you investigate a suspected pituitary tumour?
MRI of the pituitary
Visual fields
What are the three major conditions usually caused by secretions from pituitary adenomas?
Hyperprolactinaemia (prolactine excess)
Acromegaly/gigantism (GH excess)
Cushing’s disease (excess ACTH secretion)
Name some causes of hypopituitarism.
Congenital (eg Kallmann’s syndrome)
Infection (eg basal meningitis)
Vascular (eg carotid artery aneurysm)
Neoplastic (eg pituitary tumour)
What stimulates release of ACTH?
Corticotropin-releasing hormone from the hypothalamus
What does ACTH do?
Stimulates cortisol production and secretion from zone fasciculata of the adrenal cortex
What is the predominant mineralocorticoid produced in humans and where is it produced?
Aldosterone from the zone glomerulosa in the adrenal cortex
What does carbimazole do?
Inhibit formation of thyroid hormones
Is also an immunosuppressive agent
What is thyroid crisis or ‘thyroid storm’?
Rapid deterioration of hyperthyroidism with: Hyperpyrexia Severe tachycardia Extreme restlessness Cardiac failure Liver dysfunction
In the foetus what do the testis produce to promote sexual differentiation and what does it do?
Anti-Mullerian hormone
Causes atrophy of the Mullerian ducts
What do pulses of GnRH released from the hypothalamus cause secretion of?
LH and FSH from the pituitary
What does LH do in male?
Stimulate production of testosterone from Leydig cells of testis
What does FSH do in the male?
Stimulate Sertoli cells in seminiferous tubules to produce mature sperm and inhibins A and B
What does LH do in the female?
Stimulate ovarian androgen production by ovarian theca cells
What does FSH do in the female?
Stimulate follicular development and aromatase activity
Stimulate release of inhibin from ovarian stromal cells
In early puberty which gonadotropin begins to rise first?
FSH
What is precocious puberty?
Development of secondary sexual characteristics, or menarche in girls, at or before age of 9
How would you investigate precocious puberty?
LHRH/LH FSH test MRI pituitary oestradiol ovarian ultrasound Free T4 Bone age scan
What is Kallmann’s syndrome?
Isolated GnRH deficiency
usually X-linked
What is Addison’s disease?
Primary hypoadrenalism, caused by destruction of entire adrenal cortex
How are cortisol levels affected in Addison’s?
And how does this affect levels of CRH and ACTH?
Reduced cortisol, leads to increased CRH and ACTH
What causes hyper pigmentation in Addison’s?
Increased levels of CRH and ACTH
How do you treat Addison’s disease?
Long-term glucocorticoid and minerlaocorticoid replacement
What are the clinical features of Addison’s?
Hyperpigmentation Postural hypotension Weight loss Depression Malaise
What can cause secondary hypoadrenalism?
Hypothalamic-pituitary disease (inadequate ACTH production)
Long-term steroid therapy
What are the clinical features of Cushing’s syndrome?
Plethora Bruising Hypertension Weight gain Pathological fractures Striae (purple or red) Proximal myopathy
How would you confirm diagnosis of Cushing’s syndrome?
48-hour low dose dexamethasone test 24-hour urinary free cortisol measurements Circadian rhythm (cortisol blood tests)
What tests would you use to determine the cause Cushing’s syndrome?
Adrenal CT/MRI Pituitary MRI Plasma potassium levels High-dose dexamethasone test Plasma ACTH levels CRH test Chest X-ray
What causes congenital adrenal hyperplasia?
Autosomal recessive deficiency of enzyme in cortisol synthetic pathway
Most commonly 21-hydroxylase deficiency
How can severe CAH present at birth?
With sexual ambiguity or adrenal failure
How is cortisol affected in CAH and what does this cause?
Cortisol is reduced
Feedback leads to increased ACTH secretion
What is hyperaldosteronism?
Disorder of the adrenal cortex characterised by excess aldosterone production
What are the clinical features of hyperaldosteronism?
Sodium retention and potassium loss, causing hypokalaemia and hypertension
What are the main causes of primary hyperaldosteronism?
Bilateral adrenal hyperplasia (normally idiopathic)
Adrenal adenoma
What occurs in secondary hyperaldosteronism?
Excess renin stimulation of zone glomerulosa
How is bilateral adrenal hyperplasia treated?
Spironolactone (aldosterone antagonist)
What are phaechromocytomas and paragangliomas?
Rare tumours of the sympathetic NS that secrete catecholamines
How is the secretion of PTH controlled?
Plasma calcium levels
What is the effect of PTH?
Increase in serum calcium:
Increase osteoclast activity
Stimulate uptake of calcium in GIT
Enhance urinary excretion of phosphate
What causes high levels of calcitonin to be released?
Rise in serum calcium
What are the most common causes of hypercalcaemia?
Primary hyperparathyroidism
Malignancies
What are the causes of primary hyperparathyroidism?
Single parathyroid adenoma
Diffuse hyperplasia of all parathyroid glands
What is the cause of secondary hyperparathyroidism?
Physiological compensatory hypertrophy of parathyroid glands, due to hypocalcaemia caused by chronic kidney disease or vitamin D deficiency
Name some symptoms of severe hypercalcaemia.
Tiredness/malaise Dehydration Depression Renal colic (from stones) Hypertension Haematuria Bone pain Abdo pain
How would you investigate hyperparathyroidism?
Fasting serum calcium and phosphate Serum PTH Renal function 24-hour urinary calcium Abdominal X-rays Imaging for tumour (eg MRI)
How is primary hyperparathyroidism medically managed?
High fluid intake
Low calcium and vitamin D intake
Exercise encouraged
When is surgery indicated for primary hyperparathyroidism?
Renal stones/impaired renal function Bone involvement Marked hypercalcaemia Young patient (i.e. <50) Previous episode of severe acute hypercalcaemia
What are the main causes of hypocalcaemia?
Chronic kidney disease
Severe vitamin D deficiency
Post-thyroid or parathyroid surgery
Idiopathic hypoparathyroidism
How does hypoparathyroidism normally present?
Neuromuscular irritability
Neuropsychiatric manifestations
How is hypoparathyroidism normally diagnosed?
History
Clinical picture
Low serum calcium
Absent/low PTH levels
What is Conn’s syndrome?
Primary hyperaldosteronism
