NICE (The National Institute for Health and Care Excellence) has set guidelines for the assessment and management of thyroid dysfunction. These guidelines are evidence-based recommendations for healthcare professionals in various clinical and medical scenarios and can be helpful during treatment planning.

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Classification of thyroid dysfunction

Primary hypothyroidism: Primary hypothyroidism occurs when there are increased levels of serum TSH (>12mU/L) and lowered levels of serum-free Thyroxine (T4 <60 nmol/L). The possible aetiology can be the destruction of the thyroid gland because of autoimmunity or surgery, radioiodine, and radiation. Hypothyroidism is 6 times more prevalent in women. The common clinical features may include:

• Mental slowing
• Depression
• Dementia
• Weight gain
• Constipation
• Dry skin
• Hair loss
• Intolerance to cold
• Hoarseness in voice
• Oligomenorrhea
• Bradycardia
• Hypercholesterolemia

Subclinical hypothyroidism: Serum TSH is raised (>4 mU/L) whereas serum T4 is normal, with minor or no signs and symptoms of thyroid dysfunction.

Secondary hypothyroidism: Occurs in case of pituitary or hypothalamic damage, and results in insufficient production of TSH.

Thyrotoxicosis: The excess hormone is synthesised and secreted by the thyroid gland. It is characterised by normal or high uptake of radioactive iodine by the thyroid (thyrotoxicosis with hyperthyroidism or true hyperthyroidism). Thyrotoxicosis without hyperthyroidism is caused by extrathyroidal sources of thyroid hormone or by the release of preformed thyroid hormones into the circulation with a low thyroid radioactive iodine uptake.

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Indications for thyroid dysfunction test

1. Clinical suspicion of thyroid disease (although one symptom alone may not be a definitive indication).
2. Patients suffering from:
   1. Type I diabetes or other autoimmune disorder
   2. New-onset of atrial fibrillation
   3. Subjects with depression or anxiety
   4. Children and young adults with abnormal growth, or unexplained change in behaviour or school performance
   5. Menopausal women symptoms of thyroid dysfunction may also be mistaken for menopause

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1. Levothyroxine is the first-line of treatment for adults, children and young patients with primary hypothyroidism.
2. Do not routinely offer liothyronine for primary hypothyroidism. Either alone or in combination with levothyroxine, as there is insufficient data of its benefits over levothyroxine monotherapy, and its long-term adverse effects are uncertain.
3. Avoid natural thyroid extract for primary hypothyroidism as there is insufficient data of its superiority over levothyroxine, and its long-term adverse effects are uncertain.
4. Start levothyroxine with a dosage of 1.6 micro gm/kg of body weight per day (rounded to the nearest 25 micrograms) for adults under 65 yrs without a history of cardiovascular disease.
5. Start levothyroxine at a dosage of 25 to 50 micro gm per day with titration for adults aged 65 yrs and above with a history of cardiovascular disease.

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Management of subclinical hypothyroidism

1. Prescribe levothyroxine for patients with TSH level 10 mlU/litre or higher. 
2. Offer a 6-months trial of levothyroxine for adults under 65 yrs who have TSH above the reference range but <10 mlU/litre and/or symptoms of hypothyroidism.
3. If there is no improvement, re-evaluate TSH and adjust the dose.
4. If TSH is within the reference range, stop levothyroxine and follow the recommendations given below on monitoring untreated subclinical hypothyroidism:
   1. Prescribe levothyroxine for children aged 2 years and over and young adults if TSH is 20 mlU/litre or higher
   2. Offer levothyroxine for children aged between 28 days and 2 years with TSH 10 mlU/litre or higher

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Management of thyrotoxicosis

It is important to note that in transient thyrotoxicosis without hyperthyroidism, usually only supportive therapy with beta-blockers is required. Consider antithyroid drugs with supportive treatment for adults with hyperthyroidism.

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Adults with Graves’ disease

A course of antithyroid drugs can be given for 12-18 months or radioactive iodine as the first-line of definitive treatment. Plan total thyroidectomy if:

• Concerns of compression arise
• Thyroid malignancy is suspected
• Radioactive iodine and antithyroid drugs are unsuitable

Note: Consider radioactive iodine or surgery for adults who have had antithyroid drugs but have persistent or relapsed hyperthyroidism.

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Adults with toxic nodular goitre

Prescribe radioactive iodine for hyperthyroidism secondary to multiple nodules, unless it is unsuitable (like concerns about compression, thyroid malignancy, pregnancy, or active thyroid eye disease).

If radioactive iodine is unsuitable, offer total thyroidectomy or life-long antithyroid drugs. In the case of Hyperthyroidism secondary to a single nodule, offer radioactive iodine (if suitable) or surgery (hemithyroidectomy).

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Children and young adults with Graves’ disease or toxic nodular goitre

Prescribe antithyroid drugs for at least 2 years or longer. Continue or restart antithyroid drugs or radioactive iodine or surgery (total thyroidectomy) for children who have had a course of antithyroid drugs but have relapsed hyperthyroidism.

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Antithyroid drugs for adults, children and young people with hyperthyroidism

1. Check for CBC and LFT before starting antithyroid drugs for adults, children and young individuals.
2. Along with antithyroid drugs, offer carbimazole for 12 to 18 months, using either a block and replace or a titration regimen, and then review the need for further treatment.
3. Consider propylthiouracil for adults in case of:
   1. Adverse reactions to carbimazole
   2. Pregnancy
   3. History of pancreatitis

Note: Stop any antithyroid drugs if a person develops agranulocytosis and refer the patient to a specialist.

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Management of thyroid enlargement with normal thyroid function

Advice USG to image the enlargement or focal nodules if malignancy is suspected. Before making a decision about FNAC, consider an established system for grading ultrasound appearance that includes:

• Echogenicity
• Microcalcifications
• Border
• Shape in the transverse plane
• Internal vascularity
• Lymphadenopathy

Reports of ultrasound findings should include:

• Specifications of the grading system used for assessment
• An overall assessment of malignancy
• A confirmation that both lobes have been assessed
• Documented assessment of cervical lymph nodes

Note: Ultrasound guidance should be used during FNAC.

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Managing non-malignant thyroid enlargement

No treatment is indicated in non-malignant thyroid enlargements unless there is marked airway narrowing and breathing difficulty.

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When to repeat thyroid ultrasound and TSH evaluation?

If the patient's symptoms worsen or they develop symptoms of hoarseness or shortness of breath, thyroid ultrasound and TSH evaluation should be repeated. In case of a cyst or predominantly cystic nodule with no vascular components, offer aspiration if it is causing compression, with possible ethanol ablation if there is re-accumulation of cyst fluid.

For adults with normal thyroid function and a non-cystic nodule or multinodular or diffuse goitre, one of the following options can be considered, if they have compressive symptoms:

• Surgery in case of marked airway narrowing 
• Radioactive iodine ablation if there is demonstrable radionuclide uptake
• Percutaneous thermal ablation