Ep 35 – Subclinical hyperthyroidism in primary care

In this episode, Dr Kevin Fernando discusses diagnostic and management tips – as well as pitfalls to avoid – related to subclinical hyperthyroidism. Fatima is a 71-year-old woman who presents in primary care with non-specific malaise and a past medical history of atrial fibrillation, ischaemic heart disease and osteoporosis. On examination, there is no evidence of thyroid swelling. Her blood tests reveal a suppressed thyroid-stimulating hormone (TSH), but normal free thyroxine (FT4) and free triiodothyronine (FT3). Given Fatima's comorbidities, what should we do next?

Key references discussed in the episode:

• Bathgate G, Karra E, Khoo B. BMJ. 2018;362:k2880. doi: 10.1136/bmj.k2880.
• NICE. Clinical knowledge summary: hyperthyroidism. 2021. https://cks.nice.org.uk/topics/hyperthyroidism/

Key take-home messages from the episode:

• Subclinical hyperthyroidism is diagnosed when thyroid-stimulating hormone (TSH) is suppressed below the normal reference range, but free thryoxine (FT4) and free triiodothyronine (FT3) concentrations are within the normal reference range.
• Affects 5% of those aged >60 years.
• More than 50% of cases of isolated low TSH with normal free hormones will return to normal with no treatment.
• Causes include Grave’s disease, toxic thyroid nodules, thyroiditis and non-thyroidal illness. Iatrogenic causes include steroids, amiodarone, dopamine agonists, cancer immunotherapies and antiretrovirals.
• Main concern with subclinical hyperthyroidism is potential exacerbation of conditions such as atrial fibrillation, ischaemic heart disease and osteoporosis.
  • If any of these conditions present, discuss with endocrinology for consideration of treatment.