Intended for healthcare professionals

Practice Rational Testing

Investigating hypothyroidism

BMJ 2021; 373 doi: (Published 27 April 2021) Cite this as: BMJ 2021;373:n993
  1. Samantha M Siskind, internal medicine resident1,
  2. Sun Y Lee, assistant professor of medicine2,
  3. Elizabeth N Pearce, professor of medicine2
  1. 1Department of Medicine, Boston University School of Medicine, Boston, Massachusetts, USA
  2. 2Section of Endocrinology, Diabetes, Nutrition & Weight Management, Boston University School of Medicine, Boston, Massachusetts, USA
  1. Correspondence to E N Pearce Elizabeth.Pearce{at}

What you need to know

  • Suspect hypothyroidism in patients with convincing symptoms and/or signs, especially if they have risk factors for hypothyroidism, and refer them for thyroid stimulating hormone (TSH) measurement

  • An elevated serum TSH and a low serum free thyroxine are diagnostic for primary hypothyroidism, and levothyroxine, adjusted every 4-6 weeks until TSH normalises, is the treatment of choice

  • Universal screening for hypothyroidism is not recommended, as it may result in overdiagnosis, unnecessary treatment, and increased healthcare costs

A 52 year old woman presents to her general practitioner with fatigue. She started to notice feeling tired more easily and getting more sleepy during the day about eight months ago and thinks it is worsening. She also notes that she has gained 10 lbs over the past year, without major changes in her diet or exercise. Her review of symptoms is positive for constipation and increased hair loss. Her medical history includes obesity, hypertension, hyperlipidaemia, and type 2 diabetes, although her hypertension and type 2 diabetes have been well controlled on her medications. Her current medications are lisinopril, atorvastatin, and metformin. Recent laboratory tests—including a full blood count, renal function panel, liver function panel, and plasma glucose—were normal. Physical examination is notable for normal vital signs, abdominal adiposity, and dry skin, but is otherwise unremarkable.

The patient notes that her mother had hypothyroidism, and she wonders if she should be tested.


Hypothyroidism can be difficult to diagnose, as its signs and symptoms are non-specific, and no global consensus exists on screening. It can be difficult to determine when to test for hypothyroidism, as patients may present with symptoms that are subtle or that overlap with other common conditions, and guidelines can be vague regarding who and when to test. However, identification of overt hypothyroidism is important as, if left untreated, it can cause uncomfortable symptoms …

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