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CamillaSchalin-Jäntti

Examining a Patient with a Thyroid Complaint

Essentials

  • The assessment of thyroid function is primarily based on the symptoms, on clinical examination and on the measurement of TSH concentration. TSH is suitable as a screening test for dysfunction.
  • In hypothyroidism originating in the thyroid gland (primary hypothyroidism), TSH concentration is increased and free T4 (FT4) concentration is below the reference range. In hyperthyroidism, TSH is decreased (in most cases not measurable) and FT4 is above the reference range.
  • In rare hypothyroidism originating in the pituitary gland (central hypothyroidism) the serum TSH concentration is within or below the reference range and FT4 concentration is below the reference range.
  • Central hyperthyroidism is very rare. In this condition, TSH concentration is within or above the reference range and FT4 concentration is increased.
  • TSH concentration is interpreted differently in patients on thyroxine replacement therapy than in diagnostics of thyroid disorders: young patients on replacement therapy usually feel the best when TSH concentration is approximately 1-2 mU/l and FT4 concentration is near the upper threshold of the reference range. Slightly older persons may feel better when TSH concentration is in the upper part of the reference range. See also Hypothyroidism.
  • The treatment of patients with thyroid cancer is individually tailored in specialized care. The target level of THS concentration is within or below the reference range. See also Primary Care Follow-Up of Thyroid Cancer after Treatment.

History and clinical examination

Patient history

Clinical examination

  • Inspection and palpation of the thyroid gland
    • Size
      • A normal-sized thyroid gland is not palpable.
      • A clearly enlarged, large thyroid gland is already visible on inspection. The patient may experience pressure symptoms in the neck.
      • The size of the thyroid gland is assessed on palpation. Are both lobes enlarged or just one? Is the thyroid gland only slightly or markedly enlarged?
    • Consistency
      • Soft or solid? Consistency increases in Graves' (Basedow's) disease and chronic thyroiditis. In multinodular goitre, the thyroid gland is nodular.
    • Nodules (number and consistency)
      • Is there a solitary hard thyroid nodule (typical sign of thyroid cancer) or does the finding suggest e.g. multinodular goitre?
    • Tenderness
  • Heart rate
  • Possible hand tremor

Laboratory tests

  • Classification of thyroid function disorders according to basic laboratory tests: see table T1

Classification of thyroid function disorders

Biochemical criteriaClinical picture
TSH concentrationThyroid hormone concentrations
Disorders of thyroid origin
Subclinical hyperthyroidismBelow reference rangeFT4 and FT3 within reference rangeSymptomless or mild hyperthyroidism
HyperthyroidismBelow reference rangeFT4 and/or FT3 increasedHyperthyroidism
Subclinical hypothyroidismAbove reference rangeFT4 within reference rangeSymptomless or mild hypothyroidism
HypothyroidismAbove reference rangeFT4 below reference rangeHypothyroidism
Secondary disorders
Central hyperthyroidismWithin or above reference rangeFT4 and/or FT3 increasedHyperthyroidism
Central hypothyroidismWithin or slightly below reference rangeFT4 below reference rangeHypothyroidism

Thyroid-stimulating hormone (TSH)

  • Plasma TSH concentration is the basic biochemical test in the investigation of thyroid function http://www.dynamed.com/condition/hypothyroidism-in-adults#THYROID_STIMULATING_HORMONE__TSH_. The reference range in adults is approximately 0.5-4.0 mU/l but it changes with age and may vary between laboratories. Check locally relevant reference ranges for different age categories.
  • Screening for both hypo- and hyperthyroidism when the suspicion of thyroid disease is slight
    • If clinical suspicion of a thyroid function disorder is strong, it is advisable to measure FT4 concentration at the same time.
  • Subclinical primary hypothyroidism is a common finding (TSH increased, FT4 still normal); see Hypothyroidism.
  • In subclinical hyperthyroidism, TSH concentration is below the reference range but FT4 and FT3 are within the range; see Hyperthyroidism.
  • Abnormal TSH concentration does not always indicate permanent hypo- or hyperthyroidism in the following conditions (control required):
    • severe systemic diseases
    • certain drugs, e.g. high-dose glucocorticoids (reduce TSH secretion).
  • The presence of heterophilic antibodies may produce misleadingly high TSH values but with the development of the assay methods this has become rare.
  • In association with severe systemic diseases, TSH concentration may temporarily change (usually decreases) without the patient having hyperthyroidism. In the recovery phase, TSH concentration starts to increase, and thereafter it usually returns to the reference range spontaneously.
  • TSH assay is often sufficient for the follow-up of hypothyroidism if the right maintenance dose has been found and the patient feels well. Otherwise, both TSH and FT4 should be determined.

Other laboratory tests

Free thyroxine (FT4)

  • In hypothyroidism below the reference range, in hyperthyroidism above it
  • In subclinical hypothyroidism, FT4 http://www.dynamed.com/condition/hypothyroidism-in-adults#TOPIC_OTR_MKQ_JLB concentration usually is near the lower threshold of the reference range; see Hypothyroidism.
  • If hyperthyroidism is suspected on the basis of symptoms and a low TSH concentration, but FT4 is normal, free T3 (FT3) should be measured in order to detect T3 hyperthyroidism.
  • Heparin therapy and large doses of salicylates may increase and anticonvulsant drugs may decrease FT4 concentrations.

Free T3 (FT3)

  • Helpful in diagnosing borderline or incipient hyperthyroidism when TSH is unmeasurable but FT4 is within the reference range
  • FT3 assay is not used in the diagnostics of hypothyroidism.
  • FT3 is suitable for the follow-up of high-dose thyroxine therapy after thyroid cancer treatment (should be within the reference range).
  • In severe systemic diseases, FT3 concentrations are small.

TSH receptor (TSHR) antibodies

  • Encountered in Graves' (Basedow's) disease
  • Receptor antibodies either stimulate or inhibit the function of the TSH receptor. With the laboratory methods in current use it is not possible to differentiate between the antibodies according to their effect.
  • TSH receptor stimulating antibodies http://www.dynamed.com/condition/hypothyroidism-in-adults#THYROID_ANTIBODIES are found in 80-95% of patients with Graves' disease.
  • TSH receptor antibodies are measured
    • to confirm Graves' disease being behind the patient's hyperthyroidism
    • to provide further assurance of the diagnosis when the patient has the eye syndrome but not hyperthyroidism.
  • A decrease of the TSH receptor antibody concentration in patients with hyperthyroidism receiving antithyroid drug treatment is a favourable prognostic sign. The concentration remaining high when long-term antithyroid treatment is discontinued predicts recurrence of hyperthyroidism.
  • In Graves' eye disease, low TSH receptor antibody concentration suggests fading of the disease activity, and a high concentration is suggestive of inflammatory activity of the eye disease.
  • TSH receptor inhibiting antibodies are found in about 15% of patients with Graves' hyperthyroidism. In these patients, it is often difficult to find a suitable dosage for the antithyroid drug because the thyroid hormone concentrations may swing between hypothyroidism and hyperthyroidism.

Thyroid peroxidase (TPO) antibodies

  • TPO antibodies http://www.dynamed.com/condition/hypothyroidism-in-adults#THYROID_ANTIBODIES are permanently increased in common chronic autoimmune thyroiditis Chronic Autoimmune Thyroiditis which is a risk factor for hypothyroidism and the most common cause of primary hypothyroidism.
  • If the clinical problem consists of slightly increased TSH concentrations in repeated measurements but FT4 concentration remains normal, TPO antibodies should be measured. If antibodies are found, this means a higher risk of the patient developing hypothyroidism and it is advisable to start treatment more readily than in other patients.
    • Annually 5% of patients with thyroid antibodies and slightly increased TSH concentrations develop clinical hypothyroidism.
  • Chronic autoimmune thyroiditis predisposes to postpartum thyroiditis. Women with increased concentrations of TPO antibodies also have an increased risk of developing hypothyroidism during pregnancy.
  • 50-90% of patients with Graves' disease have TPO antibodies as a sign of concurrent autoimmune thyroiditis. Measurement of TSH receptor antibodies is the primary test in the investigation of Graves' disease.
  • Repeated measurements of the antibodies provide no additional value.
  • There is no use of trying to treat the increased antibody concentrations with glucocorticoids.

Imaging studies

Ultrasonography

  • The most important imaging technique of the thyroid gland http://www.dynamed.com/condition/thyroid-nodule#ULTRASOUND
  • The most important indication is the investigation of a palpable thyroid nodule or a rapidly growing thyroid gland in a euthyroid patient.
    • An ultrasonography of the thyroid nodule focuses on assessing the risk of cancer.
    • In addition to size, the composition, echo structure, shape, edges and calcifications of the lesion are assessed.
    • The findings are used to decide whether an additional fine-needle biopsy is needed to assess the risk of cancer.
  • Ultrasonography is also performed as a preoperative investigation, especially to determine the size of the thyroid gland, before planned thyroid surgery.
  • Ultrasonography has no role in examining thyroid function (in the investigation of hypo- or hyperthyroidism).
  • Thyroid ultrasonography also readily reveals very small, insignificant structural anomalies. Therefore it should not be used on too loose grounds without clear clinical question.
    • If palpation reveals a thyroid nodule in a hypo- or hyperthyroid patient, he/she should first be treated into euthyroid state and then have the palpation finding controlled.

Other imaging studies

Fine-needle biopsy

  • Fine-needle biopsy of the thyroid nodule is performed according to the criteria assessed in ultrasonography and described above here (cancer risk, size of the lesion).

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