Endocrinology Flashcards
(128 cards)
Describe thyroid cancer?
A. Papillary carcinoma
Usually contain a mixture of papillary and colloidal filled follicles. Histologically tumour has papillary projections and pale empty nuclei. Seldom encapsulated. Lymph node metastasis predominate Haematogenous metastasis rare.
B. Follicular adenoma
Usually present as a solitary thyroid nodule. Malignancy can only be excluded on formal histological assessment
C. Follicular carcinoma
May appear macroscopically encapsulated, microscopically capsular invasion is seen. Without this finding the lesion is a follicular adenoma.
Vascular invasion predominates
Multifocal disease raree
D. Medullary carcinoma
C cells derived from neural crest and not thyroid tissue. Serum calcitonin levels often raised
Familial genetic disease accounts for up to 20% cases
Both lymphatic and haematogenous metastasis are recognised, nodal disease is associated with a very poor prognosis.
E. Anaplastic carcinoma
Most common in elderly females
Local invasion is a common feature. Treatment is by resection where possible, palliation may be achieved through isthmusectomy and radiotherapy. Chemotherapy is ineffective.
what is the management of acromegaly?
- Trans-sphenoidal surgery is the first-line
If a pituitary tumour is inoperable or surgery unsuccessful then medication may be indicated:
a. somatostatin analogue
directly inhibits the release of growth hormone. for example octreotide
effective in 50-70% of patients
b. pegvisomant
GH receptor antagonist - prevents dimerization of the GH receptor
once daily s/c administration
very effective - decreases IGF-1 levels in 90% of patients to normal
doesn’t reduce tumour volume therefore surgery still needed if mass effect
c. dopamine agonists: bromocriptine
the first effective medical treatment for acromegaly, however now superseded by somatostatin analogues
effective only in a minority of patients
Describe sulfonylureas.
They work by increasing pancreatic insulin secretion and hence are only effective if functional B-cells are present. On a molecular level they bind to an ATP-dependent K+(KATP) channel on the cell membrane of pancreatic beta cells.
Common adverse effects
1. hypoglycaemic episodes (more common with long-acting preparations such as chlorpropamide)
2. weight gain
Rarer adverse effects
1. hyponatraemia secondary to syndrome of inappropriate ADH secretion
2. bone marrow suppression
3. hepatotoxicity (typically cholestatic)
4. peripheral neuropathy
Sulfonylureas should be avoided in breastfeeding and pregnancy.
Which Medications that can cause false negative renin:aldosterone ratio?
- Angiotensin-converting enzyme inhibitors (e.g. ramipril or lisinopril).
- Angiotensin receptor blockers (e.g. losartan).
- Direct renin inhibitors (e.g aliskiren).
- Aldosterone antagonists (e.g. spironolactone or eplerenone).
what are the causes of primary hyperaldosteronism?
- bilateral idiopathic adrenal hyperplasia: the cause of around 60-70% of cases.
- adrenal adenoma: 20-30% of cases (Conn’s syndrome)
- unilateral hyperplasia
- familial hyperaldosteronism
- adrenal carcinoma
features of primary hyperaldosteronism?
- hypertension
increasingly recognised but still underdiagnosed cause of hypertension - hypokalaemia
e.g. muscle weakness
this is a classical feature in exams but studies suggest this is seen in only 10-40% of patients, and is more common with adrenal adenomas - metabolic alkalosis
- Nocturnal hypertension
- Incidental adrenal mass
- Resistant oedema
7.Asymptomatic Patients
What are the investigation used for primary hyperaldosteronism?
Patients should be screened for primary hyperaldosteronism, e.g.
1. hypertension with hypokalemia
2. treatment-resistant hypertension
Investigations:
1. plasma aldosterone/renin ratio is the first-line investigation in suspected primary hyperaldosteronism
should show
↑ aldosterone and ↓renin levels (negative feedback due to sodium retention from aldosterone)
- following this a high-resolution CT abdomen and adrenal vein sampling is used to differentiate between unilateral and bilateral sources of aldosterone excess
- if the CT is normal adrenal venous sampling (AVS) can be used to distinguish between unilateral adenoma and bilateral hyperplasia
What is the management of primary hyperaldosteronism?
- adrenal adenoma: surgery (laparoscopic adrenalectomy)
- bilateral adrenocortical hyperplasia: aldosterone antagonist e.g. spironolactone
how to differentiate between primary and secondary hyperaldosteronism
Secondary Hyperaldosteronism
Unlike primary hyperaldosteronism which is caused by the autonomous overproduction of aldosterone, secondary hyperaldosteronism results from an appropriate physiological response to stimuli such as renin.
Clinically, both conditions present with hypertension and hypokalaemia.
Patients with secondary hyperaldosteronism often demonstrate signs of volume overload such as oedema or ascites.
The ↑ plasma renin activity (PRA) level is a distinguishing factor. ↑ aldosterone level
What are the causes of primary hyperparathyroidism?
85%: solitary adenoma
10%: hyperplasia
4%: multiple adenoma
1%: carcinoma
What is the differential diagnosis of hyperparathyroidism?
- Familial Hypocalciuric Hypercalcaemia (FHH) : ↓ urinary urinary calcium excretion. Thus, a
24-hour urine ca measurement can be instrumental in differentiating between this and primary hyperparathyroidism. - Malignancy-Associated Hypercalcaemia : arise from local osteolytic activity or systemic factors such as tumour production of parathyroid hormone-related protein (PTHrP).
similar biochemical profiles to primary hyperparathyroidism.
The presence of symptoms such as weight loss, fatigue and anorexia may suggest malignancy over primary hyperparathyroidism which tends to be asymptomatic or presents with non-specific symptoms like polyuria and constipation.
↓ PTH levels in malignancy-associated hypercalcaemia compared to ↑ in primary hyperparathyroidism.
- Secondary Hyperparathyroidism:
This results from increased PTH secretion in response to ↓ca and/or ↑phosphataemia.
Common causes include CKD and vitamin D deficiency.
These conditions can be differentiated from primary hyperparathyroidism by the presence of ↓ ca, ↑ phosphate levels or ↓ GFR in secondary hyperparathyroidism.
What is the management of primary hyperparathyroidism?
The 2019 NICE guidelines recommend parathyroidectomy for most patients with diagnosed primary hyperparathyroidism due to the high cure rates (up to 98%) and reduced risk of drug side effects.
Surgery is indicated for those with one or more of:
1. Symptomatic disease
2. Symptoms of hypercalcaemia
3. Osteoporosis and/or fragility fractures, Renal stones or nephrocalcinosis
4. Age <50 years
5. Serum adjusted ca of 2.85 mmol/L or above
6. Estimated eGFR of > 60 mL/min/1.73 m²
When parathyroid surgery is not acceptable, NICE recommends specialist management of hypercalcaemia with either:
- Calcitonin which reduces serum calcium concentrations by inhibiting bone and kidney resorption of calcium
- Cinacalcet which is a calcimimetic and acts to reduce serum calcium concentrations while not affecting bone density or urinary calcium concentrations
- Desunomab which also impairs calcium resorption
- Bisphosphonates
what investigation should be done for primary hyperparathyroidism?
- bloods
↑ calcium,↓ phosphate
PTH may be ↑ or (inappropriately, given the ↑calcium) normal - technetium-MIBI subtraction scan
- x-ray findings
pepperpot skull
osteitis fibrosa cystica
What is Familial hypercholesterolaemia (FH)?
autosomal dominant condition. classified as defects in the LDL receptor (most common), apolipoprotein B (ApoB), or proprotein convertase subtilisin/Kexin type 9 (PCSK9).
When we should suspect Familial hypercholesterolaemia FH?
NICE suggest that we should suspect FH as a possible diagnosis in adults with:
1. a total cholesterol level greater than 7.5 mmol/l and/or
- a personal or family history of premature coronary heart disease (an event before 60 years in an index individual or first-degree relative)
children of affected parents:
1. if one parent is affected by familial hypercholesterolaemia, arrange testing in children by age 10
2. if both parents are affected by familial hypercholesterolaemia, arrange testing in children by age 5
How is Familial hypercholesterolaemia diagnosed?
Clinical diagnosis is now based on the Simon Broome criteria:
1. in adults total cholesterol (TC) > 7.5 mmol/l and LDL-C > 4.9 mmol/l or children TC > 6.7 mmol/l and LDL-C > 4.0 mmol/l, plus:
2. for definite FH: tendon xanthoma (Achilles tendon importantly) in patients or 1st or 2nd degree relatives or DNA-based evidence of FH
- for possible FH: family history of myocardial infarction below age 50 years in 2nd degree relative, below age 60 in 1st degree relative, or a family history of raised cholesterol levels
What is the action of evolocumab in Familial hypercholesterolaemia ?
Evolocumab prevents PCSK9-mediated LDL receptor degradation. Evolocumab binds selectively to PCSK9 and prevents circulating PCSK9 from binding to the low-density lipoprotein receptor (LDLR) on the liver cell surface, resulting in reduced LDL-cholesterol.
Use of evolocumab is associated with a reduction in levels of free PCSK9 and this is taken as a measure of target engagement. it lowers LDL cholesterol by more than 50% in 85% of patients who are treated.
what is the mechanism of action of Dipeptidyl peptidase-4 (DPP-4) inhibitors (e.g. Vildagliptin, sitagliptin)?
- DPP-4 inhibitors ↑ levels of incretins (GLP-1 and GIP) by decreasing their peripheral breakdown
- oral preparation
- trials to date show that the drugs are relatively well tolerated with no increased incidence of hypoglycaemia
- do not cause weight gain
NICE guidelines on DPP-4 inhibitors
NICE suggest that a DPP-4 inhibitor might be preferable to a thiazolidinedione if further weight gain would cause significant problems
a thiazolidinedione is contraindicated or
the person has had a poor response to a thiazolidinedione
How does orlistat works?
by inhibiting gastric and pancreatic lipase to reduce the digestion of fat
Can you classify BMI?
Underweight < 18.49
Normal 18.5 - 25
Overweight 25 - 30
Obese class 1 30 - 35
Obese class 2 35 - 40
Obese class 3 > 40
What are Na levels?
mild: 130-134 mmol/L
moderate: 120-129 mmol/L
severe: < 120 mmol/L
How to treat acute (<48hypernatremia?
Hypertonic saline is normally the first-line treatment in severe hyponatremia and should be initiated in a high-dependency unit.
Normally a bolus of 150ml of 3% sodium chloride is used with repeat blood tests performed 30 minutes after the first bolus.
A 2nd bolus can be performed if an increase of 5mmol/L of sodium is not achieved.
Na+ levels are only raised by 4 to 6 mmol/l in a 24-hour period
what is Osmotic demyelination syndrome (central pontine myelinolysis)?
can occur due to over-correction of severe hyponatremia
pathophysiology:
thought to develop secondary to astrocyte (and possibly oligodendrocyte) apoptosis
astrocytes and oligodendrocytes (cells of the glial syncytium) are crucial for normal myelination
chronic hyponatraemia → loss of osmotically active organic osmolytes (such as myoinositol, glutamate, glutamine) from astrocytes. These provide protection against cerebral oedema.
organic osmolytes cannot be replaced quickly enough when the brain volume begins to shrink in response to the correction of hyponatraemia
the dehydrated astrocytes and oligodendrocytes undergo apoptosis or other forms of injury → demyelination
to avoid this, Na+ levels are only raised by 4 to 6 mmol/l in a 24-hour period
symptoms usually occur after 2 days and are usually irreversible: dysarthria, dysphagia, paraparesis or quadriparesis, seizures, confusion, and coma
patients are awake but are unable to move or verbally communicate, also called ‘Locked-in syndrome’
what MODY and its classification?
monogenic diabetes, typically autosomal dominant inheritance pattern.
HNFA = hepatocyte nuclear factor
GCK = glucokinase
MODY1 (HNF4A) (rare cause of monogenic diabetes)
MODY2 (GCK mutation)– 20% MODY3 (HNF1A mutation) – 60%
MODY4 (PDX1 or insulin gene promoter factor 1)
MODY5 (HNF1B), and so on.