Therapeutics of Thyroid Disease Flashcards
what is the thyroid gland?
The thyroid gland is located in the neck region, on the anterior surface of the trachea, just inferior (below) the larynx.
why is it important in hormoanl control?
T3 is the most active of the hormones, and when T4 is active it can also be made into T3.
T4 we give to people for treatment.
Most common thyroid disease if the primary. If you have an issue with the thyroid itself you won’t produce T3 and T4.
Secondary disease is when you have an issue in the pituitary disease and this is usually due to a whole series of other endocrine disease, you will see no TSH produced.
Tertiary disease is when you have hypothalamic disorders and it has all of the hormones cut out, this is due to a whole range of other endocrine disease.
what are the NICE guidelines/
- Published 20th November 2019
- Covers treatment of adults and children with thyroid disease
- Does not cover treatment of neonates, as covered in the national screening programme, nor pregnant women.
- The draft said it would cover pregnant women but when it was published this was changed to no longer cover them
what is primary hypothyroidism?
- At the level of the thyroid gland
- production of thyroid hormones
- Prevalence 2%, 10-20x more common in women
- 3.5% in women and 0.6% in men
what causes primary hypothyroidism?
- Autoimmune disease (Hashimoto’s thyroiditis) – this is the most common cause
- Result of previous treatment (e.g. surgery) for hyperthyroidism – removal of the thyroid
- Iodine imbalance (uncommon in UK) – this is because we have iodine in flour so it is freely available in the diet so we have less issues of low iodine levels. But worldwide this is a cause
- Congenital hypothyroidism – child born without a thyroid gland or one that is not properly functioning. 1 in 4000 children born without it.
what are the symptoms of hypothyroidism?
• Lethargy, weakness • Dry scaly skin • Sensitive to cold weather • Depression • Hair loss • Memory loss • Weight gain • Constipation • Puffy face and gruff voice with untreated disease Develops quite slowly over time and by the time you have severe hypothyroidism you would have a very swollen face and very dry hair. But, due to diagnosis improvements it usually doesn’t get to this stage anymore.
what are thyroid function tests?
Thyroid Stimulating Hormone (TSH)
Free (unbound) T4
Thyroid peroxidase antibody (rarely measured outside secondary care) – as it is an autoimmune disease
Rarely done as you can make clear diagnosis with just measuring TSH and T4
Very expensive
Primary Hypothyroidism:
• increase TSH, decrease free (unbound) T4 in the blood – pituiatary still producing TSH as they want to try and stimulate T4
how do you manage primary hypothyroidism in non-pregnant adults?
If you don’t have a very high TSH level then if you have symptoms they will trial you with medication and if this doesn’t work they will keep checking you levels and run further tests to see if there is something else that is happening to stop the pituitary gland from producing T4.
what is the initial treatment of hypothyroidism?
• Adults ≤50 years – initially 50-100 mcg thyroxine daily, adjusted 25–50 mcg every 3–4 weeks according to response
• Adults >50 years & in heart disease - initially 25 mcg once daily, adjusted 25 mcg every 4 weeks
If you rush in and give too higher a dose of T4 then you can cause heart disease or make their heart disease worse, this is why we gradually increase
• Congenital hypothyroidism – initially 10-15 mcg/kg for neonates (max 50 mcg), adjusted 5 mcg/kg every 2 weeks. S
• Measure TSH after 8-12 weeks (T½ of T4 = 7days) and three monthly until stabilised – as a child they may measure the levels more frequently to start with
what is the maintenace of hypothyroidism?
- Usual maintenance dose
- 100-200 mcg adults
- 50-200 mcg children, depending on age
- Monitor TSH yearly for adults and every 4-6 months until puberty for children; aim for
- Lower half of reference range – upper limit is 4 so you want 0.5-2 as an aim
- Symptom free
- Monitor for angina – as people get older they may not have a heart disease you know about but when you start treating them with T4 it may become apparent they do have heart disease
what are combination therapies of hypothyroidism?
- Liothyronine and levothyroxine
- Evidence shows no evidence of benefit over monotherapy
- Rarely used, usually only by endocrinologist when patient not responding to monotherapy
- Natural thyroid extract – can be bought on the internet a
- Desiccated animal thyroid gland
- Not recommended as no evidence of benefit
- Long term adverse effects uncertain – as not been on market long enough
- Source of much debate on patient forums as available in US
what are patient counselling points for hypothyroidism?
- Life-long treatment
- Single daily dose
- Do not take at same time as calcium or iron preparations or caffeine containing beverages – as it affects the absorptions
- Three strengths of tablet – common cause of confusion, they all look exactly the same usually generic
- Need for monitoring
- Entitled to medical exemption certificate for prescription charges – if you have autoimmune disease, congenital hypothyroidism.
what is hyperthyroidism?
- Autoimmune (Grave’s disease)
- Toxic Nodules
- Antibodies to TSH receptor stimulate the gland
- production of thyroid hormones
- Prevalence of 2% in women & 0.2% in men
what are the symptoms of hyperthyroidism patient?
- Anxious
- Palpitations
- Tremor
- Weight loss – relativlely quickly without trying
- Tachycardia
- Goitre
- Heat intolerance
- Warm moist skin
- Difficulty sleeping
- Diarrhoea
what are the drug therapy options for hyperthyroidism?
- Non-invasive
- Low risk of long term hypothyroidism – affecting the production of T3 and T4 rather than affecting the gland
- Low long-term cure rate (<50%) for non-mild disease, mostly used for mild disease or for people who cant take radioactive iodine or have surgery
- Rare but serious side effects requiring monitoring
- Drug therapy (thionamides) preferred for
- Children
- Pregnancy, breast feeding (propylthiouracil only)
- Uncomplicated, mild disease
- Acute phase, prior to surgery or 131I
- Carbimazole (active metabolite: methimazole) or propylthiouracil – most commonly used
- Interfere with thyroid hormone synthesis by inhibiting thyroperoxidase activity in follicular lumen
