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Investigating Thyroid Function

Why focus on thyroid function tests? Investigating Thyroid Function
When to test?
Screening patients at increased risk / asymptomatic patients
Which test should be used?
Limitations of thyroid function tests
Monitoring
Thyroid tests in the pregnant patient
Sick euthyroid syndrome
Thyroid cancer
The effects of drugs on thyroid function
GP and laboratory communication
Range of tests available
Thyroid function
References
See also TSH vs FT4: Reminder May 2007

When to test?

Despite the development of highly sensitive laboratory tests, clinical assessment and judgement remain paramount1

Key Point
Signs and symptoms provide the best indication to request thyroid tests

Initial testing for thyroid dysfunction should be based on clinical suspicion. When more of the common signs and symptoms of thyroid disease are present, there is increased prevalence of disease. In 1997, Bandolier revisited a 1978 study2 which emphasised the importance of clinical examination and history as the most significant factors when deciding to request thyroid function tests.

In the study, 500 consecutive patients were assessed for thyroid dysfunction. They were classified as high, intermediate or low suspicion of thyroid dysfunction on the basis of presenting signs and symptoms.

In the patients classified as high suspicion, 78% were subsequently identified as having a thyroid disorder. In the group with intermediate suspicion, 2.9% had a thyroid disorder, and in the group with a low degree of suspicion, 0.45% were found to have a thyroid disorder.

  Hypothyroidism Hyperthyroidism
High Suspicion Goitre
Delayed reflexes
Goitre
Thyroid bruit
Lid lag
Proptosis
Intermediate Suspicion Fatigue
Weight gain/difficulty losing weight
Cold intolerance
Dry, rough, pale skin
Constipation
Family history
Hoarseness
Fatigue
Weight loss despite increased appetite
Heat intolerance/sweating
Fine tremor
Family history
Increased bowel movements
Fast heart rate/palpitations
Staring gaze
Low Suspicion
Non specific symptoms
Coarse, dry hair
Hair loss
Muscle cramps/muscle aches
Depression
Irritability
Memory loss
Abnormal menstrual cycles
Decreased libido
Nervousness
Insomnia
Breathlessness
Light or absent menstrual periods
Weight loss
Muscle weakness
Warm moist skin
Hair loss

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