Clinical thyroid disease Flashcards
Primary thyroid disease affects which part of the hypothalamo-pituitary-thyroid axis
Thyroid gland itself
Secondary thyroid disease affects which part of the hypothalamo-pituitary-thyroid axis
The pituitary
What feedbacks and inhibits the release of TRH from the hypothalamus and TSH from the pituitary
T3 and T4
Symptoms of Hypothyroidism (10)
Weight Gain Lethargy Feeling cold Constipation Heavy periods Dry Skin/Hair Bradycardia Slow reflexes Goitre Severe – puffy face, large tongue, hoarseness, coma
Symptoms of Hyperthyroidism (10)
Weight Loss Anxiety/Irritability Heat Intolerance Bowel frequency Light periods Sweaty palms Palipitations Hyperreflexia/Tremors Goitre Thyroid eye symptoms/signs
In primary hypothyroidism what would you expect the levels of TSH and FT4 +FT3 to be like?
TSH => high
Free T4 + Free T3 => low
What is Subclinical hypothyroidism?
Earlier stage of hypothyroidism
Normal thyroxine levels
Slightly elevated TSH levels
No symptoms
It’s common for the condition to progress to full-blown hypothyroidism.
In secondary hypothyroidism what would you expect the levels of TSH and FT4 +FT3 to be like?
Low TSH (pituitary has been affected)
Low T4+T3 in blood as a result
What is the commonest endocrine condition after diabetes?
Hypothyroidism
Name 2 congenital causes of primary hypothyroidism (affecting the thyroid)
Developmental (agenesis/maldevelopment)
Dyshormonogenesis
How is primary hypothyroidism detected in babies in the UK
Through screening
Name 4 causes of acquired primary hypothyroidism
Autoimmune thyroid disease (commonest in UK)
Iatrogenic (surgery/operations, post -radioactive iodine, anti-thyroid drugs)
Chronic iodine deficiency (Commonest worldwide)
Post subacute thyroiditis - post partum thyroiditis
Causes of secondary/tertiary hypothyroidism
Pituitary / hypothalamic damage e.g
- pituitary tumour
- craniopharyngioma
- post pituitary surgery or radiotherapy
If you have a functioning pituitary what will this mean with a diagnosis of hypothyroidism?
TSH will always be elevated due to absence of negative feedback from thyroid hormones (these are low)
What investigations are carried out to diagnose hypothyroidism?
Blood tests:
- TSH/fT4
- Autoantibodies (thyroid peroxidase antibodies)
FBC
Lipids
Treatment of hypothyroidism
Levothyroxine (T4) tablets mainly - 1 x daily for rest of life
Titration method of treatment - start on high dose then reduce by 25mcg if needed
What is the half life of T4?
The half life of T4 = 7 days
When are patients brought back to the clinic for follow up blood testing after starting hypothyroidism treatment?
test every 6-8 weeks until stable then get them back for annual testing of TSH
Will be able to see if patient is being compliant
If a patient has ischaemic heart disease or is >65 y/o how should they be treated for hypothyroidism
Start them at lower dose 25mcg and increase cautiously due to risk of precipitating angina (increases metabolic rate which puts more pressure on the heart)
What is Myxoedema coma
Severe hypothyroidism leading to coma
Very rare emergency
may need IV T3
Treatment for subclinical hypothyroidism
Repeat tests after 2-3 months for Thyroxide peroxidase antibodies (to see if they have positive result)
Consider thyroid hormone treatment if TSH >10
If TSH >5 + symptoms then trial therapy for 6 months
If no symptomatic improvement stop and do annual monitoring if TPO +
Risk of osteopenia and AF in overtreatment
Treat subclinical hypothyroidism if planning pregnancy (or pregnant)
Define Osteopenia
Reduced bone mass of lesser severity than osteoporosis
How is Hypothyroidism treated during pregnancy
Increased Levothyroxine requirements during pregnancy (by about 25% - monitor closely). Aim to keep TSH in normal range <2.5 mU/l and FT4 in high normal range
Optimise treatment pre-conceptually
Inadequately treated hypothyroidism linked with increased foetal loss and Lower IQ
Causes of Goitre (5)
Physiological - Puberty, Pregnancy
Autoimmune - Grave’s, Hashimoto’s
Thyroiditis - Acute or chronic
Iodine deficiency (endemic goitre)
Dyshormogenesis
What is Hashimoto’s disease
destructive thyroiditis – eventually goes on to be hypothyroidism
Types of Goitre (4)
Multinodular
Diffuse - colloid or simple
Cystic
Tumour - adenoma, carcinoma, lymphoma
Miscellaneous - sarcoidosis, TB
Solitary nodule thyroid malignancy risk
5% chance of malignancy
increased risk if child, adult <30 or >60, previous head and neck irradiation, pain, cervical lymphadenopathy
Investigations for solitary thyroid nodule (3)
FNA - classification
Thyroid function test - it could just be a hyperfunctioning nodule
USS - differentiate if benign or malignant
From a FNA how is Thyroid cancer classified
Thy1 - inadequate
Th2 - benign
Thy5 - Cancer
What are the 2 differentiations of thyroid cancer
Papillary and Follicular
Discuss Papillary thyroid cancer
Commonest
Multifocal, local spread to lymph nodes
Good prognosis
Discuss Follicular thyroid cancer
Usually a single lesion
Metastases to lung/bone
Good prognosis if resectable
How is thyroid cancer managed initially
The main goal of thyroid cancer treatment is to get rid of all thyroid cells.
Near total thyroidectomy
After patient is given high dose of radioiodine (ablative)
Long term suppressive doses of thyroxine - depending on the cancer stage
What results in a poorer prognosis for thyroid cancer diagnosis
Age <16 or >45
Tumour size
Spread outside the thryoid capsule and metastases
TNM stage
Follow up management for thyroid cancer
Thyroglobulin => replaces levels in blood after thyroidectomy + radioiodine
Whole body iodine scanning (following 2-4 weeks of thyroxine withdrawal or recombinant TSH injections)
Anaplastic thyroid cancer
<5% of thyroid cancers
aggressive, locally invasive
very poor prognosis - doesn’t respond to radioiodine
Lymphoma thyroid cancer
Rare
May arise from preexisting hashimotos thyroiditis
External RT more helpful, combined with chemotherapy
Medullary thyroid cancer
Tumour arises from parafollicular C cells
Oftern associated with MEN 2 (phaeochromocytoma = hyperparathyroidism)
Treatment - total thyroidectomy - no role for radioiodine
In Hyperthyroidism what would you expect the levels of TSH and FT4 +FT3 to be like?
TSH low/suppressed
T3/T4 high
Causes of thyrotoxicosis
Primary - Grave’s, Toxic multinodular goitre, toxic adenoma
Secondary - pituitary adenoma secreting TSH
Thyrotoxicosis without hyperthyroidism - destructive thyroiditis, excessive thyroxine administration
What is thyrotoxicosis
Hyperthyroidism is the condition that occurs due to excessive production of thyroid hormones by the thyroid gland.
Thyrotoxicosis is the condition that occurs due to excessive thyroid hormone of any cause and therefore includes hyperthyroidism.
What is Grave’s disease
Cause of 70-80% of all hyperthyroidism cases
Autoimmune driven condition
thyroid peroxidase Antibodies
TSH receptor Antibodies
What is the most common cause of thyrotoxicosis in the elderly?
Multi-nodular goitre
Subacute (de Quervain’s thyroiditis)
Generally younger patient <50
Viral trigger (enteroviruses)
Often recall painful goitre +/- fever/myalgia
erythrocyte sedimentation rate - inflammation
May require short term steroids and NSAIDs
Patient will have a few weeks of thryotoxicosis and then months of hypothyroidism
Management of hyperthyroidism
3 possible treatments
Radioiodine
Surgery
Drugs
What can be used to help with side effects of the treatments of hyperthyroidism
Beta blockers - they slow things down
if contraindicated then sometimes use Ca2+ channel blockers
What is the main antithyroid drug used in the treatment of hyperthyroidism
Carbimazole
Which drug is used for hyperthyroidism during pregnancy
Propylthiouracil - not used otherwise due to risk of liver toxicity
Treatment regime for hyperthyroidism
Titration – starting high and then progressively decreasing dose – this method is used more often now as it has fewer side effects. (12-18 months)
Block-replace = give a block of high dose then replace with thyroxine
Radioiodine in treatment of hyperthyroidism
Can either be given in high dose ablative (more common) or variable calculated
There is a % risk of hypothyroidism after both methods
What are used to reduce the risk of thyroid eye disease due to radioiodine?
Steroids
When should radioiodine not be given
Pregnant women
Children under 18
Severe pre-existing eye disease
In Subclinical hyperthyroidism what would you expect the levels of TSH and FT4 +FT3 to be like?
TSH suppressed
Normal free thyroid hormones
the body perceives you as being in hyperthyroid state so switches off TSH but you aren’t yet
When is treatment for subclinical hyperthyroidism considered?
If it is persistent especially in elderly or those with increased cardiac risk
treatment = ATD or RAI
