Other Thyroid Conditions

Hyperthyroidism refers to the condition where the thyroid gland makes too much thyroid hormone. It is easy to diagnose with a simple blood test which shows a high T4 level and a low TSH level.

Thyrotoxicosis refers to the condition where there is too much thyroid hormone from any cause, for example, taking too many thyroid tablets.

• preference for cold
• increased appetite
• weight loss
• excessive sweating
• anxiety
• palpitations
• tiredness

1. 1. Graves’ disease
   2. Autonomous functioning thyroid nodule AFTN (autonomous hot nodule)
   3. Toxic multinodular goitre (toxic MNG)

Graves’ Disease

Graves’ disease is an autoimmune disease. A blood test shows elevated levels of TSH receptor antibodies. It typically affects middle aged (40-60 year old) females but can occur at any age and also occurs in men.

It is the most common cause of hyperthyroidism. The eyes are involved in one third of patients and the skin (pretibial myxoedema) is rarely involved.

Eye involvement includes proptosis (eyes that protrude), eye muscle involvement leading to diplopia (double vision) and optic nerve involvement leading to blindness.

Toxic Multinodular Goitre

Toxic MNG is usually seen in a long-standing goitre that slowly over time starts to secrete excessive thyroid hormone. It is usually preceded by compensated hyperthyroidism (low TSH and normal fT4 levels).

Autonomous Functioning Thyroid Nodule

This is a single thyroid nodule that is making too much thyroid hormone.

Hyperthyroidism is diagnosed with a simple blood test. The blood test shows the TSH level is low and the free T4 level is high. In Graves’ disease we also see eye signs in one third of patients and a high TSH receptor antibody level in nearly all patients. (See also thyroid blood test section in the thyroid section of this website.) 

Traditionally a radionucleotide thyroid scan is requested to differentiate between the causes of hyperthyroidism. In Graves’ disease there is diffuse homogenous uptake of the radioactive tracer. In an autonomous hot nodule, there is localised uptake of the radioactive tracer by the nodule with no uptake in the rest of the thyroid gland. In toxic multinodular goitre there is heterogenous uptake of the radioactive tracer.

An ultrasound scan can frequently differentiate between Grave’s disease, autonomous functioning thyroid nodule (AFTN), and toxic multinodular goitre. In Graves’ disease we see a homogenous (all the thyroid tissue looks the same) mild to moderately enlarged thyroid gland with a markedly increased blood flow (thyroid inferno). In AFTN we see a thyroid nodule in the setting of a low TSH and elevated fT4. In toxic MNG we see an enlarged multinodular thyroid gland in the setting of a low TSH and elevated fT4.

There are three main treatment options for hyperthyroidism:

1. Antithyroid medication. Carbimazole is the most commonly used medication (initially up to 60mg per day, then reduced slowly down to 10mg per day). Many doctors request liver function tests and a full blood count as a baseline because carbimazole may cause liver dysfunction and agranulocytosis (a blood disorder). Patients should be informed to report immediately any fever, mouth ulcers or sore throat so that urgent repeat FBC and liver function tests can be performed. Carbimazole is contraindicated in the first trimester of pregnancy. Over 50% of patients develop recurrent hyperthyroidism after stopping carbimazole. (See Thyroid Medication section.)
2. Radioactive iodine (RAI). RAI takes about 6 months to work. Following RAI, about 20% of patients develop recurrent hyperthyroidism. RAI may exacerbate eye disease in Graves’ disease. RAI is not particularly effective in large toxic multinodular goitres. Pregnancy should be avoided for 6-12 months after RAI. RAI may cause chronic sialadenitis (inflammation of the salivary glands) with a dry mouth. (See radioactive iodine section.)
3. Surgery. Surgery is very effective in Graves’ disease, autonomous hot nodules, and toxic multinodular goitre. Total thyroidectomy is recommended for both Graves’ disease and toxic MNG. Hemithyroidectomy is recommended for an autonomous functioning thyroid nodule. Surgery facilitates the treatment of Graves’ eye disease. It is important that the hyperthyroidism is controlled with antithyroid medication prior to surgery to help prevent a thyrotoxic storm. Potential complications of surgery include injury to the recurrent laryngeal nerve and hypocalcaemia. (See Thyroidectomy section.)

Finally, radiofrequency ablation (RFA) is an acceptable treatment for an autonomous hot nodule. It is a scarless procedure performed under local anaesthetic and ultrasound guidance. (See RFA section in the treatment part of the thyroid section in this website). 

Hypothyroidism occurs when the thyroid does not make enough thyroid hormone. It is easy to diagnose with a simple blood test which shows a low T4 level and a high TSH level. 

• Intolerance to cold
• Feeling tired 
• Lacking in energy
• Difficulty concentrating
• Slow thinking
• Weight gain
• Constipation 
• Depression

The most common cause of hypothyroidism is Hashimoto’s thyroiditis.

Other causes of Hypothyroidism include:

• Thyroiditis
• Iodine deficiency
• Surgery (total thyroidectomy)
• Radiation treatment to the neck
• Radioactive iodine
• Amiodarone
• Lithium
• Congenital hypothyroidism
• Pituitary disease

The pituitary gland sits under the brain and makes thyroid stimulating hormone (TSH). Therefore, if the pituitary gland is not working properly then there is not enough TSH and therefore the thyroid does not make enough thyroid hormone. This is called central hypothyroidism.

Thyroid hormones are essential for metabolism, growth and development. Therefore, if there is congenital hypothyroidism, development is affected at a very early stage. Fortunately screening for hypothyroidism in the newborn is performed with the Guthrie heel prick test. If the newborn with congenital hypothyroidism is given regular daily thyroid medication, then this newborn will develop normally. If congenital hypothyroidism is not detected in a newborn and treatment is not started immediately then this newborn will be intellectually impaired, have stunted growth, hearing and visual problems.

Hashimoto’s Thyroiditis

Hashimoto’s thyroiditis is the most common cause of hypothyroidism. Hashimoto’s thyroiditis is an autoimmune condition where the body attacks its own thyroid cells. About 50% of people with Hashimoto’s thyroiditis eventually become hypothyroid.

It is recommended that people with Hashimoto’s thyroiditis get an annual blood test to check the levels of T4 and TSH. Hashimoto’s thyroiditis may also result in an enlarged thyroid gland. There is an increased incidence of lymphoma of the thyroid gland in people with Hashimoto’s thyroiditis. In Hashimoto’s thyroiditis we see high thyroid peroxidase (TPO) antibodies. This is detected with a blood test.

As stated above the main investigation is a blood test which shows a low T4 level and a high TSH level. In Hashimoto’s thyroiditis there are elevated thyroid peroxidase (TPO) antibodies.

Hypothyroidism is treated with thyroxine tablets. Tablets are taken half an hour before breakfast every day. Approximately 1.6mcg of thyroxine per kilogram of body weight is the usual starting dose. In the elderly and patients with heart disease it is important to start at a much lower dose. After 4-6 weeks a blood test is taken to measure the levels of T4 and TSH.

The dose of thyroxine is adjusted every 4-6 weeks until the T4 and TSH levels are in the normal range. After a change in the daily dose of thyroxine it takes about 4-6 weeks for the blood levels of T4 and TSH to stabilise. Once the correct dose of thyroxine is established for an individual an annual blood test is sufficient to check T4 and TSH. (See thyroid medications section.)

Thyroiditis simply means an inflamed thyroid gland. Most forms of thyroiditis are painless. De Quervain’s thyroiditis and acute suppurative thyroiditis are painful. Pain is a very helpful symptom in distinguishing between the different types of thyroiditis.

Most types of painless thyroiditis are auto immune in nature. Hashimoto’s thyroiditis, subacute thyroiditis and Grave’s disease are all examples of thyroiditis with an autoimmune basis.  

Chronic thyroiditis is Hashimoto’s thyroiditis,  

subacute thyroiditis is either post-partum or De Quervain’s  

Acute thyroiditis is suppurative thyroiditis.

Many types of thyroiditis pass through four stages: thyrotoxicosis (too much thyroid hormone in the blood), euthyroid (a normal amount of thyroid hormone in the blood), hypothyroid (a low level of thyroid hormone in the blood) and back to euthyroid. However, one or more of these stages may not occur.

Thyrotoxicosis occurs when preformed thyroid hormones leak out of the thyroid gland into the circulation. Because antithyroid medications block the production and not the release of thyroid hormones, they are not effective in the treatment of thyroiditis. Instead, beta blockers are used to control the symptoms of thyrotoxicosis.

Graves’ disease is due to stimulation of the thyroid by thyroid stimulating antibodies causing over production of thyroid hormones (hyperthyroidism). Anti thyroid medication (carbimazole) is therefore used to treat Graves’ disease. If the decision is made to treat hypothyroidism it is treated with thyroxine at a dose of 1.6 microgram per kg per day. In elderly patients and patients with ischaemic heart disease, thyroxine is started at a lower dose, 25 micrograms per day and titrated up every 4-6 weeks depending on the results of blood tests (TSH and fT4). 

Hashimoto’s Thyroiditis (Chronic Lymphocytic Thyroiditis)

95% of patients with Hashimoto’s thyroiditis are women and it commonly presents in the 30–50 year old age group. It is the most common cause of hypothyroidism. Because about 50% of people with Hashimoto’s thyroiditis eventually develop hypothyroidism, an annual thyroid function blood test is recommended. Rarely Hashimoto’s can present with thyrotoxicosis-hashitoxicosis.

There is an increased incidence of lymphoma of the thyroid in people with Hashimoto’s. Most patients are thyroid antibody (thyroid peroxidase antibody) positive. Ultrasound scan shows an enlarged, diffusely hypoechoic, thyroid. Any suspicious nodules require ultrasound guided FNA.

Subacute Thyroiditis (Post Partum Thyroiditis)

This usually occurs 3-12 months post-partum (after giving birth). Sometimes it occurs sporadically. It presents as a small painless thyroid and symptoms of thyrotoxicosis (tachycardia, heat intolerance, nervousness, weight loss). It typically goes through the four stages discussed above. Approximately 30% of patients develop permanent hypothyroidism and require thyroxine. It is very likely (70%) to occur in subsequent pregnancies.

De Quervain’s Thyroiditis. (Subacute Granulomatous Thyroiditis)

De Quervain’s presents with pain and tenderness of the thyroid. Patients usually also complain of pain on swallowing. Geographical and seasonal (summer and autumn) clustering of cases occurs. Many viruses including mumps, echovirus, EBV, adenovirus, influenza and adenovirus have been implicated. A markedly raised ESR and raised thyroglobulin level are seen. A normal ESR or a normal thyroglobulin level rules out the condition. It typically goes through the four stages discussed above and approximately 10% develop permanent hypothyroidism and require thyroxine. The pain usually responds to high dose NSAID’s (ibuprofen up to 1800mg per day). If the pain is not controlled within four days, high dose prednisone is given. Patients may need to be on prednisone for up to 4-6 weeks before weaning slowly off prednisone.

Acute Suppurative Thyroiditis

Acute suppurative thyroiditis is uncommon. It is usually caused by Staph aureus or Strep spp. It is associated with either immunosuppression or a fistula of the pyriform sinus. It presents in a systemically unwell patient with fever and a tender enlarged thyroid lobe. The overlying skin may be erythematous (red). Blood tests show the ESR and CRP are elevated. Treatment is with antibiotics.

There should be a low threshold to request an ultrasound which may reveal an abscess. Any abscess should be drained surgically. Subsequent elective hemithyroidectomy plus or minus excision of any associated fistula may be required.  Pharyngoscopy (looking at the throat) may reveal the opening of a fistula in the pyriform fossa (third and fourth arch congenital branchial cleft fistula).

Reidel’s Thyroiditis

Reidel’s thyroiditis presents as a bony hard thyroid mass. About one third of patients develop other areas of fibrosis including sclerosing cholangitis, retroperitoneal fibrosis or orbital pseudotumour. Diagnosis is with a biopsy. Sometimes hemithyroidectomy is required to make the diagnosis.

Treatment is symptomatic or surgical, depending on the severity of the symptoms, and the certainty of diagnosis. Excising the thyroid isthmus may be enough to relieve symptoms in some patients. Medical treatment with prednisone, mycophenolate or tamoxifen has been tried.

Graves’ Disease

See hyperthyroidism section of the thyroid section in this website.

Drug Induced Thyroiditis

Several drugs may induce thyroiditis. Amiodarone and lithium are probably the best-known drugs to induce thyroiditis. Other drugs that can induce thyroiditis include immune check point inhibitors and tyrosine kinase inhibitors.

Radiotherapy and RAI may also induce thyroiditis.

Thyroiditis Summary

Thyroiditis is best categorised by the presence or absence of pain. Pain from De Quervain’s is treated with high dose NSIAD’s or prednisone. Some patients with thyroiditis develop permanent hypothyroidism. Surgery is reserved for patients with a thyroid abscess, symptoms from an enlarged thyroid or as definitive treatment of Graves’ disease and some cases of drug induced thyroiditis.

References:

1. Quintero BM, et al. Thyroiditis evaluation and treatment. American Family Physician 2021; 104: 609-617.  
2. Lafontaine N, et al. Suppurative thyroiditis: systematic review and clinical guidance. Clin Endocrinology 2021; 95: 253-264.  
3. Ragusa F, et al. Hashimoto’s thyroiditis: epidemiology, pathogenesis, clinic and therapy. Best Practice & Research Clin Endo & Metab. 2019; 33:  

A thyroglossal duct cyst is a midline neck cyst formed from an embryological remnant of the thyroid near the hyoid bone. Between the fifth and seventh weeks of gestation, the thyroid descends from the tuberculum impar, at the foramen caecum in the back of the tongue to its location in the lower neck.

The track of descent may pass anterior (in front of), posterior (behind) or through the hyoid bone as the thyroid descends from the back of the tongue to the lower neck, After descent this track involutes (disappears). Sometimes this track does not fully involute and a cyst containing thyroid tissue near the hyoid may persist. This cyst is called a thyroglossal duct cyst.

Other Thyroid Remnants

Thyroid tissue may be left anywhere along this tract from the base of the tongue to the thyroid. A lingual thyroid, sublingual thyroid and a pyramidal lobe are all examples of thyroid tissue remaining in this tract.

Lingual Thyroid

A lingual thyroid is a thyroid lump on the back of the tongue. They are very uncommon. They enlarge in pregnancy. If they enlarge, they can cause blockage of the airway. Small lingual thyroids may be treated with thyroxine tablets which help suppress any growth. Large lingual thyroids will need excising either through the mouth or through the neck.

Most large lingual thyroids are highly suitable for transoral robotic surgery. Before excising a lingual thyroid, it is important to check if there is any other thyroid tissue by doing an ultrasound. If there is no other thyroid tissue, then the patient will need to take thyroxine tablets lifelong.

A thyroglossal duct cyst usually presents in a child or young adult but may present at any age. They may be entirely asymptomatic. It is thought that they become infected through communication with the pharynx (throat). When a thyroglossal duct cyst becomes infected, the cyst increases in size and becomes sore. The overlying skin may become inflamed and sometimes the cyst may spontaneously burst through the skin and discharge.

A thyroglossal duct cyst presents as a midline neck mass under the jaw. It moves when the patient swallows. Sometimes the cyst is a short distance (1cm) from the midline. Usually the cyst is small, about 1-2 cm in size, but occasionally it may become quite large (4-6cm).

Ultrasound Scan of a Thyroglossal Duct Cyst

An ultrasound scan of a thyroglossal duct cyst will show a mass in the vicinity of the hyoid bone. This mass may be either cystic, solid or both. Before operating, it is important to ensure that there is thyroid tissue in the normal location. If there is no other thyroid tissue, then the patient will need to take thyroxine tablets lifelong.

Differential Diagnosis of a Thyroglossal Duct Cyst

An enlarged lymph node, a midline dermoid and a lipoma may all be clinically mistaken for a thyroglossal duct cyst. A careful history, physical examination and ultrasound will help make the diagnosis of a thyroglossal duct cyst. An ultrasound guided FNA may further clarify any confusion. Although it has been said that there is a higher incidence of malignancy in ectopic thyroid tissue, this is a rare occurrence.  

Some surgeons recommend excision of all thyroglossal duct cysts to prevent episodes of inflammation. Asymptomatic thyroglossal duct cysts require no treatment.

The treatment of an infected thyroglossal duct cyst is antibiotics and pain medication. It is important that the antibiotic covers anaerobic bacteria. Amoxicillin and clavulanic acid (Augmentin, Curam Duo) are good choices. If the patient gets worse, the infected cyst will need to be drained. This is best done with the minimal of disruption to the surrounding tissues. Ultrasound guided needle drainage or free hand drainage of the cyst with an 18-gauge needle is recommended. The fluid aspirated is sent for culture and sensitivities. If the patient is still getting worse, then incision and drainage is recommended again taking care to minimise disruption to the surrounding tissues.