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Hypothyroidism Care Pathway Overview

Hypothyroidism is the clinical result of impaired production of thyroid hormones; thyroxine (T4) and tri-iodothyronine (T3). Thyroid hormones are released from the thyroid gland when it is stimulated by thyroid-stimulating hormone (TSH) from the anterior pituitary.

  • Primary hypothyroidism occurs when the thyroid gland is unable to produce thyroid hormones because of iodine deficiency or an abnormality within the gland itself. It is categorized as:
    • Overt hypothyroidism (OH) — thyroid-stimulating hormone (TSH) levels are above the normal reference range (usually above 10 mU/L) and Free Thyroxine (T4) is below the normal reference range.
    • Subclinical hypothyroidism (SCH) — thyroid-stimulating hormone (TSH) levels are above the normal reference range and tri-iodothyronine (T3) and Free Thyroxine (T4) are within the reference range.
  • Secondary or central hypothyroidism is the result of insufficient production of bioactive thyroid-stimulating hormone (TSH) due to a pituitary or hypothalamic disorder.
  • Postpartum thyroiditis (PPT) is the development of thyrotoxicosis, hypothyroidism, or thyrotoxicosis followed by hypothyroidism within a year of giving birth in women who were euthyroid prior to pregnancy.

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Red Flags
Admit anyone with symptoms of Myxoedema coma;
  • Typical features of hypothyroidism with hypothermia, coma and occasionally seizures
  • Refer using suspected 2ww Head and Neck Cancer pathway if a person has a non toxic thyroid nodule or goitre. 
Note: thyroid function tests are usually normal in people with thyroid cancer
Presentation

Symptoms and signs of hypothyroidism may be subtle and non-specific — some people (especially the elderly) may be asymptomatic.

  • Symptoms may include:
    • Fatigue/lethargy.
    • Cold intolerance.
    • Weight gain.
    • Non-specific weakness, arthralgia, and myalgia.
    • Constipation.
    • Menstrual irregularities.
    • Depression, impaired concentration, and memory.
    • Dry skin, and reduced body and scalp hair (such as sparse eyebrows).
    • Thyroid pain, for example in subacute (de Quervain’s) thyroiditis.
  • Signs may include:
    • Changes to appearance such as coarse dry hair and skin and hair loss.
    • Oedema, including swelling of the eyelids.
    • Vocal changes such as hoarseness or deepening of the voice.
    • Goitre.
    • Bradycardia and diastolic hypertension.
    • Delayed relaxation of deep tendon reflexes.
    • Paraesthesia — due to carpal tunnel syndrome.

Symptoms and signs include those of primary hypothyroidism with or without those associated with:
  • An intracranial mass such as headache, diplopia, or reduced peripheral vision.
  • Abnormal pituitary hormone production such as skin depigmentation, atrophic breasts, galactorrhoea, amenorrhoea, erectile dysfunction, loss of body hair, Cushing’s syndrome, or acromegaly.

  • The hypothyroid phase of Postpartum thyroiditis (PPT) usually occurs between 3–8 months (most often at 6 months) postpartum and lasts typically 4–6 months.
Differential Diagnosis

A number of conditions may cause similar symptoms and signs to hypothyroidism. These include:

Initial Primary Care Assessment

  • Thyroid-stimulating Hormone (TSH)
  • Consider checking Free Thyroxine (FT4) if on Amiodarone, lithium, if possible pituitary dysfunction (Note: In ICE select appropriate reason from the pick-list and FT4 will be added to the TSHDiscussion with the duty biochemist may be helpful to clarify.
  • Thyroperoxidase (TPO) may be useful if Thyroid-stimulating Hormone (TSH) suggests subclinical hypothyroidism . However this test has poor specificity for a clinically significant thyroid disorder.
  • Note: most patients with borderline raised TSH will not progress to overt hypothyroidism over 5 years and TSH will normalise. TPO will be assayed only once. Repeated analysis is not indicated.

  • Family history of thyroid or autoimmune disease
  • Autoimmune disorders: Type 1 diabetes, Addison’s disease and pernicious anaemia etc.
  • Down’s or Turner Syndrome
  • Radiotherapy to the neck
  • Radioiodine treatment or previous thyroid surgery for hyperthyroidism
  • Iodine deficiency
  • Amiodarone or lithium use

  • Signs of hypothyroidism such as;
    • Weight gain
    • Coarse facies
    • Hair loss
    • Lethargy
    • Bradycardia
    • Diastolic hypertension
    • Delayed relaxation of deep tendon reflexes
  • Goitre and/or thyroid nodules
  • Enlarged cervical lymph nodes
  • Signs of carpal tunnel syndrome
  • Signs of other autoimmune disease such as vitiligo

                                           

 

Diagnose/suspect hypothyroidism

  • Thyroid-stimulating Hormone (TSH) is greater than 10 mU/L and Free Thyroxine (FT4) is below the reference range.

  • Thyroid-stimulating Hormone (TSH) is above the reference range and Free Thyroxine (FT4) is within the reference range. (Note: FreeT4 assay is not routinely useful if TSH is less than 10 mU/L)
  • In non-pregnant people repeat Thyroid-stimulating Hormone (TSH) 6 months after the initial result to exclude transient causes of a raised Thyroid-stimulating Hormone (TSH) and to confirm the diagnosis of Subclinical Hypothyroidism (SCH).

  • Clinical features are suggestive and Free Thyroxine (FT4) is low without raised Thyroid-stimulating Hormone (TSH).
    Be aware that in secondary hypothyroidism Thyroid-stimulating Hormone (TSH) may also be low, normal, or slightly elevated due to circulation of bio-inactive forms of Thyroid-stimulating Hormone (TSH).

  • Thyroid-stimulating Hormone (TSH) is elevated (using trimester-specific reference ranges, which may vary locally).

  • Thyroid-stimulating Hormone (TSH) is raised within a year of giving birth.
Initial Primary Care Management

  • Overt hypothyroidism (OH) should be treated with levothyroxine initially low dose and titrate according to TSH, aiming for TSH 0.4-2.5 mU/L - all people who are stable on levothyroxine (LT4) require at least annual measurement of serum Thyroid-stimulating Hormone (TSH) levels. Note: a rise in thyroid function may unmask previous non symptomatic cardiac disease. This must be treated before further rises in levothyroxine.
  • Subclinical hypothyroidism (SCH) depends on the specific clinical situation – in some cases a ‘watch and wait’ approach may be appropriate. If a decision is made to treat, prescribe levothyroxine (LT4). Aim (in most people) to reach a stable Thyroid-stimulating Hormone (TSH) level in the lower half of the reference range (0.4–2.5 mU/L).

  • Consideration of prescribing of Liothyronine (T3) should only be made by an NHS Endocrinologist for patients with:
    • Thyroid cancer, and that these prescriptions should come from the centre providing the cancer treatment
    • An allergy to Levothyroxine (T4)

Transfer from out of county already taking this medication.

See the Gloucestershire Joint Formulary for further information on Thyroid and antithyroid drugs.

If any uncertainty consider referral via Advice and Guidance

  • Check Thyroid Function Tests (TFT) before conception if possible
  • If Thyroid Function Tests (TFT’s) abnormal, advice delaying pregnancy until stabilised on Levothyroxine (LT4) – discuss with endocrinology via Advice and Guidance if uncertainty about treatment
  • Ensure that the woman understands that her dose of Levothyroxine (LT4) must be adjusted as early as possible in pregnancy to minimise future obstetric and fetal complications

  • with well controlled hypothyroidism:
    • Refer to Obstetrics

 

  • with poorly controlled hypothyroidism / previous thyrotoxicosis:
    • Refer to Medical Antenatal Clinic
When to Refer

Urgent referral to an endocrinologist should be arranged if Secondary hypothyroidism is suspected.

 

Consider referral to Endocrinology for patients with:

  • Adverse effects from treatment with levothyroxine (LT4).
  • Significant cardiac disease.
  • Abnormal thyroid gland structure, atypical thyroid function tests, or an unusual cause of hypothyroidism (for example due to drugs such as amiodarone).
  • Persistent symptoms despite treatment with levothyroxine (LT4).
  • Consideration of the prescribing of Liothyronine (T3) with or without T4 should only be made by an NHS Endocrinologist

 

If patient is planning pregnancy (see Initial Primary Care Management section above)

 

If patient is pregnant with well controlled hypothyroidism:

  • Refer to Obstetrics

 

If patient is pregnant with poorly controlled hypothyroidism / previous thyrotoxicosis:

  • Refer to Medical Antenatal Clinic

 

Women with postpartum thyroiditis (PPT)

  • If not settling discuss with secondary care
Ongoing Primary Care Management

Follow up of people with Subclinical Hypothyroidism (SCH) who are started on levothyroxine (LT4)

  • Reassess symptoms on treatment. If symptoms have improved, lifelong treatment may be considered. If symptoms have not improved or if adverse effects are reported, stop levothyroxine (LT4) after a 3–6 month trial.
  • Once Thyroid-stimulating Hormone (TSH) has normalized, Thyroid Function Tests (TFT) should be measured at least annually thereafter.
  • If lipids were elevated at initial assessment, recheck to see if they have improved adequately or the person needs therapy for dyslipidaemia.

Follow up of people with Subclinical Hypothyroidism (SCH) who are started on levothyroxine (LT4) and Liothyronine (T3)

  • Suggest biochemical monitoring annually. Patients should be reviewed clinically at 3 months to see if symptoms improved – if not consider discontinuing T4 but monitor annually

Follow up of people with Subclinical Hypothyroidism (SCH) who are not started on levothyroxine (LT4)

  • If Thyroid-stimulating Hormone (TSH) has normalized without treatment, no further testing is needed if the person is asymptomatic, and does not have a goitre.
  • If Thyroid-stimulating Hormone (TSH) remains elevated, arrange repeat Thyroid Function Tests (TFT) every 6 months for the first 2 years and then annually.
  • Arrange annual Thyroid Function Tests (TFT) in people with Subclinical Hypothyroidism (SCH) who are thyroid peroxidase antibody (TPOAb) positive or have a goitre.
  • Arrange repeat Thyroid Function Tests (TFT) every 3 years in people with Subclinical Hypothyroidism (SCH) who are TPOAb negative.
  • If lipids were elevated at initial assessment, recheck these to see if the person needs treatment for dyslipidaemia.
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