Dr. SK Wangnoo as part of a new exclusive endocrinology series on hyperthyroidism throw spotlight on presentation of the thyroid hyperfunction among different age groups, risk factors involved, and possible complications primary care physicians should be aware of.

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Hyperthyroidism is a condition in which an overactive thyroid gland produces an excess amount of thyroid hormones that circulate in the blood.(Hyper means over in Greek). The thyroid hormones include thyroxin (T4) and triiodothyronine (T3). T3 is actually the most active thyroid hormone. Much of the T4 is converted to T3 in the blood stream.

The thyroid gland is a butterfly-shaped gland located in the front of the neck. The gland is regulated by the pituitary gland in the brain and the pituitary gland in turn is regulated by the hypothalamus in the brain.

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Thyrotoxicosis

Thyrotoxicosis is a term where the causes of over-production of thyroid hormones are 'extra-thyroidal'. The causes of thyrotoxisosis could be:

• Drug-induced (amiodarone, interferone alpha, programmed death receptors 1 (PD-1), and lithium), or,
• Factitious due to ingestion of excess thyroid hormones, or,
• Very rarely it could be ectopic hyperthyroidism due to thyroid cancer metastasis and struma ovarii (on ovarian tumour that contains thyroid tissue)

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What are the symptoms and signs?

Hyperthyroidism leads to a wide variety of symptoms and signs like:

• Weight loss despite normal appetite
• Rapid heart rate (tachycardia); commonly more than 100 beats/minute or irregular heart beat (arrhythmias)
• Increased appetite and more frequent bowel movements, nausea and vomiting
• Anxiety, nervousness, irritability, fine finger tremors on outstretched hands, increased sweating and heat intolerance
• Easy fatigability, insomnia, muscle weakness and fine brittle hair
• Menstrual irregularities in females
• Dyspnoea or shortness of breath
• Heat intolerance and polydipsia
• Excessive sweating, sweaty palms
• Poor concentration, disturbed sleep

Older adults might have very subtle signs and symptoms. Some patients have a visible enlarged thyroid gland (goitre) which might be tender to touch in cases of painful acute thyroiditis. Patients where the underlying cause is Graves', may present with protruding eyeballs (called proptosis) and watery eyes.

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Common causes

1. Graves' disease: It is an autoimmune disorder in which antibodies produced by your immune system (TSH receptor antibody, TRAB) stimulate your thyroid to produce too much T4.
2. Toxic adenoma/toxic multinodular goitre (TMNG): It presents as single adenoma (benign) or multiple lumps (adenoma) in the glands.
3. Thyroiditis: Sometimes, the thyroid gland may be inflamed after a viral infection (viral thyroiditis) or after pregnancy (post-partum thyroiditis) which is usually a transient condition and spontaneous resolution of symptoms may occur in 4-6 weeks time.

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Risk factors to consider

Some of the important risk factors for development of hyperthyroidism include:

• Family history of Grave’s disease
• Female gender
• History of type 1 diabetes, adrenal insufficiency and pernicious anaemia

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What complications should physicians be aware of?

Here are some of the complications a physician should be aware of in a patient with hyperthyroidism:

1. Complications related to the cardiovascular system- Rapid heart rate (tachycardia), disorders of heart rhythm (atrial fibrillation) and congestive heart failure.
2. Eye complications- Bulging (proptosis) of eyes, redness, lid swelling, blurring or double vision. If not treated on time can lead to vision loss.
3. Dermatological complications- Redness and swelling over the skin called Graves' dermopathy and brittle nails.
4. Musculoskeletal system complications- Muscle weakness, hypokalemia, periodic paralysis and brittle bones (osteoporosis).
5. Genitourinary complications- Gynaecomastia in males and menstrual irregularities in females.
6. Gastrointestinal complications- Dysphagia, or orthopnoea due to oesophageal or tracheal compression in nodular goitre.

Untreated patients might present with “thyrotoxic crisis” – an endocrine emergency presenting with fever, tachycardia, heart failure and delirium. It needs immediate medical attention.

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Hyperthyroidism- Pregnancy and post-partum

The most common causes of hyperthyroidism in pregnancy is Graves' which needs treatment with anti-thyroid drugs; however there is also gestational thyrotoxicosis which is a benign and transient disorder and needs just symptomatic treatment. Post-partum thyroiditis which come under the spectrum of PPTD (post-partum thyroid disorders) is again a transient phase and needs just symptomatic management.

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Hyperthyroidism in children

Hyperthyroidism is a rare but serious disorder in childhood, occurring most frequently as a consequence of Graves’ disease (GD), an autoimmune disorder. Acute or subacute thyroiditis, chronic lymphocytic thyroiditis, acute or chronic administration of thyroid hormones and/or iodides may also result in transient thyrotoxicosis.

In infants, symptoms and signs of hyperthyroidism include irritability, feeding problems, hypertension, tachycardia, exophthalmos, goitre, frontal bossing, and microcephaly. Other early findings are failure to thrive, vomiting, and diarrhoea.

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General practitioners should be aware of common clinical presentations and related complications of hyperthyroidism in order to treat them at an early stage. This is an attempt to give a “birds eye view” of thyroid hyperfunction and its common clinical signs symptoms and complications.

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This is first of the series on hyperthyroidism, and it will be followed by two other article which will cover diagnostic modalities, management of hyperthyroidism and thyroid eye disease.

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Disclaimer- The views and opinions expressed in this article are those of the author's and do not necessarily reflect the official policy or position of M3 India.

The authors of this article are Dr. Subhash Kumar Wangnoo and Dr. Tarunika Bawa.