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Dilemma: Doubt over thyroxine prescription

Set out pointers about how you practise

At this first consultation I would set down pointers to demonstrate how I practise. I feel that if I do not deal with these issues now, it will be much more difficult to change later.

First, I would say that for any condition where medication is lifelong, care has to be taken when making the diagnosis. I would suggest she stops the medication and has blood tests six weeks later, including tests for thyroid antibodies.

Second, I would point out that thyroxine could cause palpitations or diarrhoea, plus unseen side-effects such as osteoporosis.

Third, I would explore other potential causes of her original symptoms – such as anaemia and diabetes – as well as assessing for depression and chronic fatigue syndrome. I would look at any psychosocial issues in follow-up consultations.

Finally, I would discuss that sometimes private doctors look at issues differently from NHS ones. Sometimes NICE guidelines are not adhered to and expensive branded products are prescribed, but I would not be critical of another doctor.

I would say that I always review prescriptions from a private doctor and give examples from my recent practice. If the blood tests confirm she has hypothyroidism then I would prescribe thyroxine on the NHS. If the TFTs are normal then I would look for an alternative diagnosis.

Dr Steve Brown is a GPSI in ENT and a GP trainer in Buckinghamshire

Explain that your medical practice is evidence based

To be diagnosed as hypothyroid, it is essential that thyroid function is tested biochemically alongside a careful clinical assessment of the individual patient. Clinical symptoms or signs alone are insufficient to make a diagnosis. The serum TSH assay is an exquisitely sensitive test for identifying patients with any degree of primary hypothyroidism.

As thyroid hormone production decreases, serum TSH increases. The decrease in thyroid hormone secretion may be small and not sufficient to reduce the T4 concentration below the reference range (subclinical hypothyroidism or mild thyroid failure), followed by a fall in serum T4, at which stage most patients have symptoms and benefit from treatment (overt hypothyroidism).

A normal serum TSH thus excludes primary, but not secondary, hypothyroidism. It would be important to obtain her menstrual history and consider and exclude hypopituitarism.

It will be necessary to explain that your medical practice is evidence based. There are no data to support the use of levothyroxine in patients with normal thyroid function and you should emphasise that you are not prepared to continue this prescription even if she has had an initial improvement. This improvement is unlikely to be sustained as you do not believe thyroid failure is the cause of her symptoms. I suggest slowly withdrawing levothyroxine over two months and re-assessing her, with investigation if her symptoms return.

Dr Mark Vanderpump is a consultant physician and honorary senior lecturer in diabetes and endocrinology at the Royal Free London NHS Foundation Trust

Check the diagnosis with the private physician

It is unclear what diagnosis the private physician made to justify prescribing thyroxine. GPs are responsible for all the prescriptions they issue, so if you are in doubt as to whether she has a condition that would benefit from thyroxine, investigate before prescribing.

This is in line with the GMC’s guidance on prescribing, which says you should prescribe medicines ‘only if you have adequate knowledge of the patient’s health and you are satisfied that they serve the patient’s needs’.

So long as you have no reason to believe that the patient might be harmed by stopping her prescription, you may need to decline this woman’s request until you are able to speak to her private physician.

If the physician is unable to explain the reasons to your satisfaction, explain to the patient you are unable to re-issue the prescription. Discuss with her whether there might be other treatments to help with her symptoms. If she is unhappy with your decision, she can request a second opinion from a local specialist or continue to see the private physician, ideally keeping you informed of any ongoing treatments.

If your conversation with the private physician raises any concerns about patient safety, talk to a senior colleague or your medical defence organisation, as the GMC places a positive duty on doctors to raise such concerns.

Dr Phil Zack is a medicolegal adviser at the Medical Defence Union

Further reading

• NICE. Clinical Knowledge Summaries: hypothyroidism. 2011

• Royal College of Physicians. The diagnosis and management of primary hypothyroidism, 2011

• GMC. Good practice in prescribing and managing medicines and devices, 2013


Editor’s Note

For a clinical dilemma article like this, especially one regarding a prescribing decision, we would typically ask the opinion of three people: a GP (preferably one with a relevant clinical specialism), a consultant and someone from a medical defence organisation.

Due to a breakdown in communication, two GPs and a non-medical representative of Thyroid UK were initially commissioned - and so the decision was made to recommission some of the elements. Our medical adviser had expressed a preference for Dr David Lewis’ contribution to be retained but asked for some revisions to be made to it.

Unfortunately Thyroid UK informed us that by that point Dr Lewis was too ill to edit his section, so we chose Dr Steve Brown, a GP with a special interest in ENT medicine, to be the GP voice. Dr Mark Vanderpump, a regular contributor to Pulse’s clinical section, supplied the secondary care perspective and Dr Phil Zack from the MDU provided advice from a medico-legal standpoint.

We understand the subject of subclinical hypothryoidism and its treatment is a very emotive one; however the clinical advice contained in the article is based on current UK clinical guidance. The elements of the article which were originally commissioned but which we were unable to use were not omitted because of any agenda on the part of the Pulse editorial team, but simply because the Dilemmas series follows a very specific format, which the first draft did not fit.

Adam Legge
Group clinical editor