Endocrinology Flashcards
Primary hypoparathyroidismGraves’ Disease features exclusive
eatures seen in Graves’ but not in other causes of thyrotoxicosis
* Eye signs: exophthalmos, ophthalmoplegia
* Pretibial myxedema
* Thyroid acropachy
Graves’ Disease antibodies
Autoantibodies
* Anti-TSH receptor stimulating
antibodies (90%)
* Anti-thyroid peroxidase
antibodies (50%)
Graves treatment
ATD titration
* Carbimazole is started at 40mg and ↓ gradually to maintain euthyroidism
* Typically continued for 12-18 months
* Patients following an ATD titration regime have been shown to suffer fewer side-effects than those
on a block-and-replace regime
Block-and-Replace
* Carbimazole is started at 40mg
* Thyroxine is added when the patient is euthyroid
* Treatment typically lasts for 6-9 months
The major complication of carbimazole
agranulocytosis (pancytopenia)
Radioiodine Treatment
* Contraindications
pregnancy (should be avoided for 4-6 months following treatment) and age < 16 years. Thyroid eye disease is a relative contraindication, as it may worsen the condition
Thyrotoxicosis causes
Causes
* Graves’ disease
* Toxic nodule goitres
* Subacute (de Quervain’s) thyroiditis
* Post-partum thyroiditis
* Acute phase of Hashimoto’s thyroiditis (later results in hypothyroidism)
* Toxic adenoma (Plummer’s disease)
Thyrotoxicosis labs
- TSH down, T4 and T3 up
- Thyroid autoantibodies
- Other investigations are not routinely done but includes isotope scanning
Toxic Multinodular Goitre
describes a thyroid gland that contains a number of
autonomously functioning thyroid nodules that secrete excess thyroid hormones. Nuclear scintigraphy
reveals patchy uptake. The treatment of choice is radioiodine therapy
Thyroid Storm
rare but life-threatening complication of thyrotoxicosis. It is typically seen in patients with established thyrotoxicosis and is rarely seen as the presenting feature. Iatrogenic thyroxine excess does not usually result in thyroid storm
Tyroid storm - Clinical features include:
- Fever > 38.5oc
- Tachycardia
- Confusion and agitation
- Nausea and vomiting
- Hypertension
- Heart failure
- Abnormal liver function test
Tyroid storm Management
Symptomatic treatment e.g. Paracetamol
* Treatment of underlying precipitating event
* Anti-thyroid drugs: e.g. Methimazole or propylthiouracil
* Lugol’ s iodine
* Dexamethasone - e.g. 4mg IV QDS - blocks the conversion of T4 to T3
* Propranolol
Subacute Thyroiditis (De Quervain’s Thyroiditis)
thought to occur following viral infection and typically presents with hyperthyroidism
Features
* Hyperthyroidism
* Painful goiter
* Raised ESR
* Globally ↓ uptake on iodine-131 scan
Subacute Thyroiditis (De Quervain’s Thyroiditis)
Management
Management
* Usually self-limiting - most patients do not require treatment
* Thyroid pain may respond to aspirin or other NSAIDs
* In more severe cases steroids are used, particularly if hypothyroidism develops
Hashimoto’s Thyroiditis
Features
Features
* Features of hypothyroidism
* Goitre: firm, non-tender
* Positive microsomal antibodies, anti-thyroid peroxidase (Anti-TPO) and anti-Tg antibodies.
Subclinical Hyperthyroidism
Normal T3 – T4
* ↓ TSH (usually < 0.1 mu/l)
Causes
* Multinodular goitre, particularly in elderly ♀s
* Excessive thyroxine may give a similar biochemical picture
importance in recognising subclinical hyperthyroidism
effect on the cardiovascular system (atrial fibrillation) and bone metabolism (osteoporosis). It may also impact on quality of life and ↑ the likelihood of dementia
Subclinical Hyperthyroidism Management
Management
* TSH levels often revert back to normal - therefore levels must be persistently low to warrant
intervention
* A reasonable treatment option is a therapeutic trial of low-dose antithyroid agents for
approximately 6 months in an effort to induce a remission
Subclinical Hypothyroidism
Normal T3 – T4
* ↑TSH
* No obvious symptoms
Subclinical Hypothyroidism
Significance
Significance
* Risk of progressing to overt hypothyroidism is 2-5% per year (higher in men)
* Risk ↑ by presence of thyroid autoantibodies
Subclinical Hypothyroidism
Treat if
* TSH>10
* Thyroid autoantibodies positive
* Other autoimmune disorder
* Previous treatment of graves’ disease
Hypothyroidism
Causes:
Causes:
Hypothyroidism affects around 1-2% of women in the UK and is around 5-10 times more common in ♀s than ♂s.
In European countries primary atrophic hypothyroidism is the most cause causes of
hypothyroidism, whereas in North America Hashimoto’s thyroiditis appears to account for the
majority of cases. The reason for this discrepancy is unclear
Primary hypothyroidism
Primary atrophic hypothyroidism
2. Hashimoto’s thyroiditis
3. After thyroidectomy or radioiodine treatment
4. Drug therapy (e.g. lithium, amiodarone or anti-thyroid drugs such as carbimazole)
5. Dietary iodine deficiency
Primary atrophic hypothyroidism
Most common cause in Europe
* Autoimmune disease, associated with IDDM, Addison’s or pernicious anemia
* 5 times more common in women
Hashimoto’s thyroiditis
Autoimmune disease as above with goitre (Anti-TPO) * May cause transient thyrotoxicosis in the acute phase
* 10 times more common in women
Secondary hypothyroidism (rare)
- From pituitary failure
- Other associated conditions
* Down’s syndrome
* Turner’s syndrome
* Coeliac disease
Hypothyroidism treatment
- Initial starting dose of levothyroxine should be lower in elderly patients and those with ischemic heart disease (e.g. 25–50 mcg/day).
- Following a change in thyroxine dose thyroid function tests should be checked after 6-8 weeks
- The therapeutic goal is ‘normalisation’ of the thyroid stimulating hormone (TSH) level. As the majority unaffected people have a TSH value 0.5–2.5 mu/l it is now thought preferable to aim
for a TSH in this range. Dosage changes should of course also take account of symptoms - There is no evidence to support combination therapy with levothyroxine and liothyronine
Side-effects of thyroxine therapy
- Hyperthyroidism: due to over treatment
- ↓ bone mineral density
- Worsening of angina
- Atrial fibrillation
thyroid function - Thyrotoxicosis (e.g. Graves
TSH low
T4 high
In T3 thyrotoxicosis, T4 will be normal
thyroid function -Primary (atrophic) hypothyroidism
TSH high
T3/4 low
thyroid function - Secondary hypothyroidism
TSH low
T3/4 low
Steroid therapy is required prior to thyroxine
thyroid function - Sick euthyroid syndrome*
TSH low
T3/4 low
thyroid function - Poor compliance with thyroxine
TSH high
T3/4 normal - high
thyroid function - Steroid therapy
TSH Low
T3/4 normal
Pendred’s Syndrome
Autosomal recessive disorder of defective iodine uptake
Features:
* Sensorineural deafness
* Goitre
* Euthyroid or mild hypothyroidism
Skin Manifestations of Thyroid Diseases:Hyperthyroidism
Pretibial myxedema: erythematous, edematous lesions above the lateral malleoli
* Thyroid acropachy: clubbing
* Scalp hair thinning
* ↑ sweating
Skin Manifestations of Thyroid Diseases:Hypothyoridism
Dry (anhydrosis), cold, yellowish skin
* Non-pitting edema (e.g. Hands, face)
* Dry, coarse scalp hair, loss of lateral
aspect of eyebrows
* Eczema
* Xanthomata
Propylthiouracil
antithyroid drug of choice in pregnancy. This
approach was supported by the 2007 Endocrine Society consensus guidelines. It also has the
advantage of being excreted to a lesser extent than carbimazole in breast milk.
Pregnancy: Thyroid Problems
pregnancy there is ↑ in the levels of thyroxine-binding globulin (TBG). This causes ↑ in the levels of total thyroxine but does not affect the free thyroxine level
Pregnancy: Thyrotoxicosis
ntreated thyrotoxicosis ↑ the risk of fetal loss, maternal heart failure and premature labour
* Graves’ disease is the most common cause of thyrotoxicosis in pregnancy. It is also recognised that activation of the TSH receptor by HCG may also occur - often termed transient
gestational hyperthyroidism. HCG levels will fall in second and third trimester
Pregnancy Hypothyroidism
- Thyroxine is safe during pregnancy
- Serum thyroid stimulating hormone measured in each trimester and 6-8 weeks post-partum
- Some women require an ↑ dose of thyroxine during pregnancy
- Breast feeding is safe whilst on thyroxine
Thyroid Cancer:
Papillary 70%
Follicular 20%
Medullary 5%
Anaplastic 1%
L ymphoma Rare
Thyroid Cancer:Papillary 70%
Often young ♀s - excellent prognosis (associated with FAP)
Thyroid Cancer:Follicular 20%
Spreads through blood vessels
Thyroid Cancer: medullary
Cancer of parafollicular cells, secrete calcitonin, part of MEN-2
Thyroid Cancer L ymphoma
Associated with Hashimoto’s and other autoimmune disorders
Management of papillary and follicular cancer
- Total thyroidectomy
- Followed by radioiodine (I-131) to kill residual cells
- Yearly thyroglobulin levels to detect early recurrent disease (only after total thyroid ablation)
Primary Hyperparathyroidism
elderly ♀s with an unquenchable thirst and an inappropriately normal or raised parathyroid hormone level. It is most commonly due to a solitary adenoma
Causes of Primary Hyperparathyroidism
Causes of primary hyperparathyroidism
* 80%: solitary adenoma
* 15%: hyperplasia
* 4%: multiple adenoma
* 1%: carcinoma
Feature of Primary Hyperparathyroidism
Features:
‘Bones, stones, abdominal groans and psychic moans’
* Polydipsia, polyuria
* Peptic ulceration/constipation/pancreatitis
* Bone pain/fracture
* Renal stones
* Depression
* Hypertension
Association of Primary Hyperparathyroidism
Associations
* Hypertension
* Multiple endocrine neoplasia: MEN I and II
Investigations Primary Hyperparathyroidism
nvestigations
* Raised calcium, low phosphate
* PTH may be raised or normal
* Technetium-MIBI subtraction scan
Treatment Primary Hyperparathyroidism
IV Fluids
* Total parathyroidectomy
* Bisphosphonates
Primary hypoparathyroidism
↓ PTH secretion
* E.g. Secondary to thyroid surgery
* Low calcium, high phosphate
* Treat with alfacalcidol
Pseudohypoparathyroidism
Target cells being insensitive to PTH
* In type I pseudohypoparathyroidism there is a complete receptor defect whereas in type II the
cell receptor is intact.
* Due to abnormality in a G protein
* Autosomal dominant fashion*
* Associated with low IQ, short stature, shortened 4th and 5th metacarpals
* Low calcium, high phosphate, high PTH
* Diagnosis is made by measuring urinary cAMP and phosphate levels following an infusion of
PTH. In hypoparathyroidism this will cause ↑ in both cAMP and phosphate levels. In pseudohypoparathyroidism type I neither cAMP nor phosphate levels are ↑ whilst in pseudohypoparathyroidism type II only cAMP rises.
Pseudopseudohypoparathyroidism
Similar phenotype to pseudohypoparathyroidism but normal biochemistr
Diabetes Insipidus - Cranial DI causes
- Idiopathic
- Post head injury
- Pituitary surgery
- Craniopharyngiomas
- Histiocytosis X
DIDMOAD
association of cranial Diabetes Insipidus, Diabetes Mellitus, Optic Atrophy and Deafness (also known as Wolfram’s syndrome)
Causes of nephrogenic DI
- Genetic (primary)
- Electrolytes: hypercalcemia, Hypokalemia
- Drugs: demeclocycline, lithium
- Tubulo-interstitial disease: obstruction, sickle-cell, pyelonephritis
Diabetes Insipidus investigations
High plasma osmolarity, low urine osmolarity
* Water deprivation test
Water Deprivation Test Normal
starting os Normal (275-299)
Final urine os > 600 HIGH
Urine os post DDVAVP - > 600 HIGH
Psychogenic polydipsia water dep results
starting os LOW
Final urine os > 400
Urine post DDAVP >400
Cranial DI Water Deprivation Test
starting os HIGH
Final urine os <300 LOW
Urine post DDAVP <600 HIGH
Water Deprivation Test Nephrogenic DI
starting os HIGH
Final urine os <300 LOW
Urine post DDAVP <300 LOW
Diabetes Mellitus
f the patient is symptomatic:
* Fasting glucose ≥7.0 mmol/l
* Random glucose ≥11.1 mmol/l (or after 75g oral glucose tolerance test)
If the patient is asymptomatic the above criteria apply but must be demonstrated on two separate occasions.
Impaired fasting glucose (IFG):
fasting glucose 6.1 - 7.0 mmol/l implies impaired fasting glucose
Impaired glucose tolerance (IGT)
fasting plasma glucose < 7.0 and OGTT 2-hour 7.8 - 11.1
Sulfonylureas
increasing pancreatic insulin secretion (B cells must be present)
Sulfonylureas Common adverse effects
Hypoglycaemic episodes (more common with long acting preparations such as chlorpropamide)
* ↑ appetite and weight gain
Sulfonylureas should be avoided in breast feeding and pregnancy
Metformin CI
Chronic kidney disease: NICE recommend reviewing metformin if the creatinine is > 130
μmol/l and stopping metformin if > 150 μmol/l
* Do not use during suspected episodes of tissue hypoxia (e.g. Recent MI, sepsis)
* Alcohol abuse is a relative contraindication
* Stop 2 days before general anaesthetic, restart when renal function normal
* Stop prior to IV contrast e.g. Angiography, restart when renal function norm