Thyroid disease Flashcards
What does a structural assessment of the thyroid gland involve?
Assessing size of thyroid;
Normal
Reduced or absent
?Ectopic
Enlarged - Goitre
Physiological
Pathological
What are the physiological reasons for thyroid gland enlargement?
Adolescence
Pregnancy
What does a functional assessment of the thyroid involve?
Assessing how well it’s functioning;
Euthyroid
Hypothyroid (Underactive)
Hyperthyroid (Thyrotoxic)
What is the preferred imaging technique for the thyroid?
USS
When does the foetal thyroid develop and start thyroxine production?
By week 12, thyroxine production by week 16.
Why is maternal thyroid supply important in a foetus?
Helps neurological development
Which developmental problems can there be with the thyroid gland?
Congenital hypothyroidism
Aberrant/Ectopic thyroid gland
Thyroglossal cyst
What does a TFT involve?
Testing for TSH, FT4 and FT3.
Which hormones are affected in hypothyroidism?
TSH high
FT4 low
Which hormones are affected in hyperthyroidism?
TSH low
FT4 and FT3 high
TSH is the initial investigation of choice. When would T4 + T3 be tested?
Secondary/central hypothyroidism
Non-thyroidal illness
Recent treatment for thyrotoxicosis
Does TSH respond quickly to changes in the thyroid?
No, takes around 6 weeks for levels to be stable when there have been changes to the thyroid.
What are the normal serum levels for TSH, FT4 and FT3?
TSH - 0.3-3.5 mU/L
FT4 - 10-25 pmol/L
FT3 - 3.5 - 7.5 pmol/L
What specific symptoms and signs are there of hypothyroidism?
Cold intolerance
Facial puffiness
Dry skin
Hair less
Hoarseness
Heavy menstrual periods
Bradycardia
Stupor or coma
What risk factors are there for hypothyroidism?
Other autoimmune conditions e.g. T1DM or coeliac
Family history
Immune therapy for cancer - melanoma
What can happen to the thyroid in postpartum?
Patients can develop postpartum thyroiditis 8-20 weeks postpartum.
After treatment for which condition can hypothyroidism occur?
Thyrotoxicosis
- if post surgery or post radioiodine
What is the difference between primary and secondary hypothyroidism?
Primary - high TSH, low T4 + T3. No negative feedback loop to reduce TSH.
Secondary - Low TSH, T4 + T4. Disease of pituitary or hypothalamus.
Which form of hypothyroidism is rare?
Secondary
What are the two types of hypothyroidism?
Primary and secondary
What are some causes of primary hypothyroidism?
Autoimmunity
Infection (thyroiditis)
Drug interactions
Congenital hypothyroidism
Iodine deficiency
Post hyperthyroidism treatment
What are some causes of secondary hypothyroidism?
Pituitary tumours
Tumours compressing hypothalamus
Sheehan syndrome
TRH resistance
TSH deficiency
Lymphocytic hypophysitis
Radiotherapy
How is hypothyroidism treated?
Levothyroxine (T4)
Liothyronine (T3) - less commonly. Short half life.
What is the half life of levothyroxine?
7-10 days
Why should the elderly generally have a lower dose of levothyroxine?
There is a risk of CCF
When should TSH be tested after starting levothyroxine?
After 4-6 weeks. Keep level around 2 mU/L
If someone is taking levothyroxine, does their dosage change in pregnancy?
Yes - increases by 25-30%
What can happen in severe hypothyroidism?
Myxoedema
- Endocrine emergency - high mortality
What are the clinical features of a myxoedema?
Decreased mental status and hypothermia
Bradycardia
Hypotension
Hypoglycaemia
Myxoedematous face - peripheral oedema
How is myxoedema treated?
Supportive management - ITU
IV levothyroxine + occasionally T3
IV Hydrocortisone 200-400mg daily
What are the specific symptoms of hyperthyroidism?
Weight loss
Shakes
Palpitations
Loose bowels
What are some causes of hyperthyroidism (Thyrotoxicosis)?
Graves disease (autoimmune)
Thyroiditis
Toxic multi nodular goitre
Toxic adenoma
Drug induced
Which drugs can cause thyrotoxicosis?
Amiodarone
Lithium
Which eye problem can thyrotoxicosis present with?
Thyroid eye disease
Which biochemical changes can be seen in thyrotoxicosis?
Liver - Transaminitis (AST, ALT, ALT)
Bone - High ALP, hypercalcaemia
Pancytopenia or neutropenia
Why does Graves disease occur?
Autoantibody (Ig) binds to thyroid epithelial cells, mimicking the stimulatory action of TSH.
Binds to TSH receptor, and increases thyroid activity.
This causes T4 + T3 to increase and the thyroid to grow –> goitre.
What are the symptoms of thyroid eye disease?
Inflammation of orbital tissues (not the eye)
Itchy, dry eyes
Prominent eyes
What are the signs of thyroid eye disease?
Diplopia/loss of sight
Loss of colour vision
Redness and swelling of conjunctiva
Inability to close eyes
Aching and pain behind eyes
What is the name for when eyes are protruding?
Proptosis
What is a toxic adenoma?
Abnormal growth - ‘nodule’ either solid or fluid filled.
Generates excess thyroid hormones.
Usually benign.
What is a toxic multi nodular goitre?
Multiple nodules in the thyroid that generates excess thyroid hormones.
Usually benign.
What are the five types of thyroiditis?
De Quervain’s thyroiditis
Postpartum - autoimmune
Drug induced - damages thyroid tissue
Radiation indued
Acute/infectious
What causes De Quervain’s thyroiditis?
Viral infection.
Painful.
How is hyperthyroidism treated?
Medication - Carbimazole or Propylthiouracil
What can happen is hyperthyroidism is not treated?
Symptoms escalate e.g. Graves disease
AF
Osteoporosis
What is the MOA of Carbimazole and Propylthiouracil?
Inhibit thyroid peroxidase leading to a reduction of T4 and T3.
How long is the medical treatment of hyperthyroidism usually for?
18-24 months to reduce the risk of relapse
Which dangerous side effect can occur with Thyroid peroxidase inhibitors (Carbimazole and Propylthiouracil)?
Agranulocytosis
High mortality, takes 2 weeks to resolve.
Sore throat, mouth ulcer and infection.
What two options are there for treating hyperthyroidism with Carbimazole?
Start high then reduce as thyroid function settles
Continue high dose then add thyroxine
How does I131 Radiotiodine (RAI) treat hyperthyroidism?
I131 concentrates in thyroid
B radiation destroys the cells to make thyroid euthyroid or hypothyroid.
Can a total or sub-total thyroidectomy for hyperthyroidism when a patient is still hyperthyroid?
No - patient needs to be euthyroid first.
What are some risks of a total or sub-total thyroidectomy?
Hypothyroidism
Hypoparathyroidism
Vocal cord palsy (recurrent laryngeal nerve damage)
How is a thyroid adenoma or multi-toxic goitre treated?
Medical treatment to control thyroid function then curative treatment with I131.
How is thyroid eye disease treated?
To treat thyrotoxicosis;
Immunosuppressants
Steroids
Radiotherapy
To treat eye;
Orbital decompression
Eye surgery
Which rare complication can there be in Grave’s disease that has a high mortality risk?
Thyroid storm (thyrotoxic crisis)
What can trigger a thyroid storm?
Surgery
Pregnancy
Acute severe illness
What are the symptoms of a thyroid storm (thyrotoxic crisis)?
Hyperpyrexia
CVS - Tachycardia >140bpm, arrhythmia, HF
CNS - Low GCS, agitation, delirium
GI - Nausea/vomiting, deranged LFTs
What is the management of a thyroid storm?
Supportive treatment
B-blockers for tachycardia
Antithyroid medication - Propylthiouracil (PTU) - prevents peripheral conversion of T4 to T3
Iodine solution
Steroids and bile acid sequestrant
What are the common causes of goitres?
Hashimoto thyroiditis
Graves disease
Familial or sporadic multi nodular goitre
Iodine deficiency
Follicular adenoma
Colloid module or cyst
Thyroid cancer
What increases the risk of a goitre developing?
Malignancy
Family history
<20 or >60
Male
Radiation exposure
What is involved in the palpation of a thyroid examination?
Hands - erythema hot or cold
Face - coarse facies
Eyes - exophthalmos
Trunk - Proximal myopathy (hyper/hypothyroid)
Legs - Pretibial myxoedema (Graves’ disease), brisk or slow relaxing reflexes
Percussion and auscultation
What dose of Carbimazole is usually given for thyrotoxicosis?
FT4 <30pmol/L - 20mg OD
FT4 >30pmol/L - 40mg OD
What are the two types of Auto antibodies?
Destructive - target the thyroid
Stimulatory - Target TSH receptor
TPO antibodies increase the risk of developing what in the next 10 years?
Hypothyroidism
Which antibody can cause thyroid diseases?
TSH receptor antibody
Why is surgery not done unless a patient is euthyroid?
Risk of thyroid storm - removing thyroid will release hormones into circulation.
CVS risk due of anaesthetic due to increases hormones
