Treatment of thyroid disorders Flashcards
(35 cards)
What are the abnormalities of Thyroid function ?
Hypothyroidism (‘underachieve’ thyroid)
- Inadequate production and secretion of thyroid hormones (T3 and T4)
Hyperthyroidism (‘overactive’ thyroid)
- Excessive production and secretion of thyroid hormones (T3 and T4)
When do we do thyroid function tests (TFT’s)?
Consider performing TFT’s’
- If clinical suspicion of thyroid disease
- Type 1 diabetes or other autoimmune diseases
- New onset atrial fibrillation (cause of hyperthyroid)
- In depression or unexplained anxiety
- Weight changes
How do we treat thyroid disorders in general (not medically) ?
Treatment of thyroid disorders;
- Thyroid conditions usually respond well to treatment
- The aim of treatment is to improve symptoms and return thyroid function to within or close to the reference range
- Patients may feel well even when their TFT’s are outside the reference range
- Treatment is usually still recommended for asymptomatic patients with abnormal TFT’s to reduce the risk of long-term complications
- Symptom improvement may lag behind treatment changes (this can take weeks to months)
What are the features of Hypothyroidism?
Hypothyroidism;
- Decreased serum free Thyroxine (T4)
- Increased thyroid stimulating hormone (TSH)
- Found approximately in 2-5% of the UK population
- Females are 5 - 10 times more like to be affected than males
Long term complications of hypothyroidism include;
- Cardiovascular disease
- Goitre
- Myxodema coma (very rare but life threatening)
What are the features of Subclinical Hypothyroidism?
Subclinical Hypothyroidism;
- Biochemical state where TSH is raised but T3 and T4 are within the reference ranges
- Often detected incidentally although some people may experience symptoms
- Prevalence 4-20%
Long term consequences;
- Increased risk of Cardiovascular mobility and mortality
- Increased risk of fractures and potential links to dementia
What are the symptoms of Hypothyroidism?
Symptoms of Hypothyroidism;
- Tiredness
- Weight gain
- Feeling cold
- Constipation
- Dry or thinning hair
- Hoarse voice
- Pins and needles
- Low mood
- Memory problems
What are the causes of Hypothyroidism?
Causes of Hypothyroidism;
- Autoimmune thyroiditis - Hashimoto’s
- Congenital
- Iatrogenic (e.g post thyroidectomy or radio-iodine treatment)
- Drug induced (e.g anti-thyroid medications, lithium, amidarone)
- Pituitary disease
What are the features of Hasimoto’s?
Hashimoto’s;
- Most common cause of hypothyroidism
- Autoimmune lymphocytes thyroiditis
- An anti body against thyroglobulin is produced or one which has antagonist effects at follicular TSH receptors
- Females > Males
How common is Congenital Hypothyroidism (CHT) and the causes?
Congenital Hypothyroidism (CHT);
1 in 2000-3000 babies are born with CHT in the UK (Part of heel prick test in babies)
Causes;
- Absent thyroid (agenesis)
- Under-developed thyroid (dysgenesis) - more common in girls
- Familial enzyme defects (dyshormonogenesis)
- Iodine deficiency
- Intake of goitrogens during pregnancy
- Pituitary defects
- Idiopathic
What are the features of Newborns with Congenital Hypothyroidism ?
- May have few or no clinical manifestations of thyroid deficiency
- All babies screened at birth (heel prick test)
- Untreated CHT can result in impaired brain development and low IQ
- If treatment started before the baby is 2-3 weeks old the likelihood of significant longterm problems is low
What are the features of Amiodarone?
Amiodarone;
- Amiodarone has a very close structural resemblance to thyroid hormones
- The free base contains 39% iodine by weight, and longterm treatment is associated with 40-fold increase in plasma and urinary iodide levels
- Patients can develop Amiodarone induced hypothyroidism or thyrotoxicosis therefore monitoring of TFT’s is important
How do we treat Primary Hypothyroidism?
Treatment Primary Hypothyroidism;
- Levothyroxine (synthetic analogue of thyroxine - T4)
- Do not routinely offer liothyronine for primary hypothyroidism due to lack of evidence
- Natural thyroid extract does not have UK marketing authorisation so safety is unknown
- Staring dose Levothyroxine is 1.6 micrograms/kg of body weight per day (rounded to the nearest 25 micrograms) for adults < 65 years old with primary hypothyroidism and no history of cardiovascular disease (If start at higher dose can exacerbate cardio issues so start low in elderly)
- For patients > 65 years old and adults with history of cardiovascular disease consider starting Levothyroxine at 25 - 50 micrograms per day with titration as higher dose could exacerbate underlying cardiac disease
- Aim to maintain TSH levels within the reference range
- After start or dose check recheck TFT’s after 6 weeks
What is the treatment for Subclinical Hypothyroidism ?
Treatment for Subclinical Hypothyroidism;
- Recommendation is to consider Levothyroxine in adults with TSH > 10mU/L on 2 separate occasions 3 months apart
Consider a 6 month trial or Levothyroxine for adults < 65 years old with subclinical hypothyroidism who have:
- A TSH level above the reference range but <10mU/L on 2 separate occasions 3 months apart who are experiencing symptoms of hypothyroidism
How should we monitor Hypothyroid patients?
Consider measuring TSH every 3 months until the level has stabilised and then yearly
What are the features of Hyperthyroidism ?
Hyperthyroidism;
- Raised T3 and T4 and low TSH
- About 10 times more common in females than males
- Typically affects people ages 20-40 years old
What is important to do when considering diagnosing Hyperthyroidism ?
Need to differentiate between Thyrotoxicosis with hyperthyroidism (e.g graves or toxic nodular disease) and thyrotoxicosis without hyperthyroidism (e.g transient thyroiditis ) by;
- Measuring TSH receptor antibodies (TRAbs) to confirm Graves
- Consider technetium scanning of the thyroid gland if TRAbs are negative
How would you treat Transient Thyrotoxicosis without Hyperthyroidism?
Treatment of Transient Thyrotoxicosis without Hyperthyroidism;
- Only needs support treatment (e.g beta blockers - Propranolol best options for symptoms of tremor, sweating, palpitations, etc)
What are the causes of Hyperthyroidism ?
Causes of Hyperthyroidism;
- Autoimmune - Grave’s disease
- Toxic multi-nodular goitre
- De Quervain’s - (subacute) thyroiditis
- Medication (over-treatment of Levothyroxine)
- Pituitary adenoma (tumour producing excess TSH)
- Transient neonatal thyrotoxicosis (mother with Graves)
- Thyroid adenoma (rare)
What are the features of Grave’s disease?
Grave’s Disease;
- Autoimmune disorder mediated by antibodies that stimulate TSH
- Accounts for 60-80% of cases of thyrotoxicosis caused by hyperthyroidism
- Guidelines recommend measuring TSH receptor antibodies (TRAbs) in patients with thyrotoxicosis to confirm Grave’s disease
- Most common in women aged 30-60 years old
Clinical features;
- Diffuse goitre
- Pretibial myxoedema
- Thyroid eyed ease (prominent eyes due to decomposition of myxoedema behind the orbit)
- Arcopachy (swelling of distal digits with overgrown nail plates - different to clubbing)
What are the features of Toxic Multinodular Goitre ?
Toxic Multi-nodular Goitre;
- Small benign nodules within the thyroid gland. Cells within the nodules are unresponsive to secretary control mechanisms and secrete excess T3 and T4
- Worldwide, iodine deficiency is the most common cause
What are the features of de Quervain’s syndrome?
Subacute thyroiditis;
- Painful swelling of thyroid gland
- Triggered by a viral infection
- Most commonly seen in women aged 20 - 50
What are the symptoms of Hyperthyroidism ?
Symptoms of Hyperthyroidism;
- Anxiety
- Palpitations
- Weight loss
- Goitre
- Hair loss
- Fatigue
- Diarrhoea
- Sweating
- Muscle weakness
- Insomnia
- Periods lighter/infrequent
How do we treat Hyperthyroidism ?
Treatments of Hyperthyroidism;
- Radioactive iodine
- Anti-thyroid medication
- Symptomatic medication
- Surgery
Important to discuss risk and benefits of all with patient
What are the features of Radioactive iodine?
Radioactive iodine;
- Radioactive iodine is given orally and selectively taken up by the thyroid
- Half life of 8 days
- Given as a dose and lasts approximately 2 months
- When administered it is accumulated by follicular cells and as it decays the beta particles emissions destroy surrounding tissue. Since the path length of particles if only 0.5-1mm the damage is restricted to follicular cells
- Usually not suitable before puberty
- Hypothyroidism eventually occurs which can be treated with replacement therapy
- Avoid contact with pregnant women and small children (small risk of radiation)
