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