Hyperthyroidism

Iodine 131 when taken up by thyroid gland result in destruction of the trapping cell and cells in close proximity.

Because thyroid gland has extremely high affinity for iodine compared to other tissues, radioactive iodine results in selective ablation of thyroid tissue.

Ref: Diseases of the Thyroid in Childhood and Adolescence By Gerasimos E. Krassas, Volume 11, Page 172; Encyclopedia of Diagnostic Imaging By Albert L. Baert, Volume 1, Page 452; Iodine an Overview, Page 18.

Explanation: During molar pregnancy there is a large amount of circulating HCG which shares a structural resemblance to TSH which is responsible for the hyperthyroidism in molar pregnancy.

Chronic thyroiditis or Hashimoto’s disease is a common hypothyroid disorder. It can occur at any age, but is most often seen in middle-aged women. It is caused by a reaction of the immune system against the thyroid gland.The disease begins slowly. It may take months or even years for the condition to be detected.

Chronic thyroiditis is most common in women and people with a family history of thyroid disease. It affects between 0.1% and 5% of all adults in Western countries.Hashimoto’s disease may, in rare cases, be associated with other endocrine disorders caused by the immune system. Hashimoto’s disease can occur with adrenal insufficiency and type 1 diabetes. In these cases, the condition is called type 2 polyglandular autoimmune syndrome (PGA II).

Ans. is ‘b’ i.e., Propanolol

Answer is D (Grave’s Disease):

Grave’s disease is the single most common cause for Hyperthyroidism and Thyrotoxicosis.

Ans. B: Propranolol

Beta-blockers such as propranolol help control many of the symptoms of hyperthyroidism.

These drugs can slow a fast heart rate, reduce tremors, and control anxiety.

Beta-blockers are particularly useful for people with extreme hyperthyroidism and for people with bothersome or dangerous symptoms that have not responded to other treatments.

However, beta-blockers do not reduce excess thyroid hormone production.

Therefore, other treatments are added to bring hormone production to normal levels.

Ans. A: Prophyltiouracil

Though effective in pregnant women, babies of mothers taking antithyroid drugs have a high risk of goiter, hypothyroidism or even cretinism.

However, low doses of propylthiouracil is preferred in pregnancy: its greater protein binding allows less transfer to the fetus. For the same reason it is to be preferred in the nursing mother.

Ans. B: Delayed deep tendon reflexes

Features of hyperthyroidism

• Increased heat production – warm, moist skin, heat intolerance
• Telangiectasia, palmar erythema, pretibial myxoedema, onycholysis
• Weight loss, increased appetite, increased frequency of bowel movement but frank diarrhoea is uncommon.
• Oligomenorrhoea
• Tachycardia, exertional dyspnoea, hyperdynamic circulation; systolic hypertension is common and diastolic
• hypertension can occur in up to 30% of patients
• Tiredness, irritability, nervousness
• Fine tremor, hyperkinesias, hyperreflexia, muscle wasting
• There are eye signs in Graves’ disease

Others:

• Occasionally, bone pain due to osteoporosis
• In elderly patients, there may be atrial fibrillation or cardiac failure
• Alopecia, pruritus, pretibial myxoedema, acropachy (form of clubbing)

Atypical presentation may include:

• Atrial arrhythmias in middle aged patients
• Severe proximal myopathy with normal CK values
• Deterioration or unmasking of myasthenia gravis
• Hypokalaemic periodic paralysis – especially in orientals
• Chronic diarrhoea
• Hypercalcaemia
• Osteoporosis
• Gynaecomastia

Ans. B: Cold intolerance

Causes

Functional thyroid tissue producing an excess of thyroid hormone occurs in a number of clinical conditions. The major causes are:

– Graves’ disease (the most common etiology with 70-80%)

– Toxic thyroid adenoma

– Toxic multinodular goitre

High blood levels of thyroid hormones/hyperthyroxinemia can occur for a number of other reasons:

–   Inflammation of the thyroid is called thyroiditis. There are a number of different kind of thyroiditis including Hashimoto’s (immune mediated), subacute (inflammatory), and DeQuervain’s (granulomatous). These may be initially associated with secretion of excess thyroid hormone, but usually progress to gland dysfunction and thus, to hormone deficiency and hypothyroidism.

– Struma ovarii (a teratoma of the ovary) can produce excess thyroid hormone.

– Amiodarone, a heart medication, can sometimes cause hyperthyroidism.

– Postpartum thyroiditis (PPT) occurs in about 7% of women.

Major clinical signs include weight loss (often accompanied by a increased appetite), anxiety, intolerance to heat, fatigue, hair loss, weakness, hyperactivity, irritability, apathy, depression, polyuria, polydipsia, and sweating. Additionally, patients may present with a variety of symptoms such as palpitations and arrhythmias (notably atrial fibrillation), shortness of breath (dyspnea), loss of libido, nausea, vomiting, and diarrhea.

Long term untreated hyperthyroidism can lead to osteoporosis

Neurological manifestations can include tremor, chorea, myopathy, and in some susceptible individuals (particularly of asian descent) periodic paralysis.

Minor ocular (eye) signs, which may be present in any type of hyperthyroidism, are eyelid retraction (“stare”) and lid-lag.

In hyperthyroid stare (Dalrymple sign) the eyelids are retracted upward more than normal (the normal position is at the superior corneoscleral limbus, where the “white” of the eye begins at the upper border of the iris).

In lid-lag (von Graefe’s sign), when the patient tracks an object downward with their eyes, the eyelid fails to follow the downward moving iris, and the same type of upper globe exposure which is seen with lid retraction occurs, temporarily. These signs disappear with treatment of the hyperthyroidism.

Neither of these ocular signs should be confused with exophthalmos (protrusion of the eyeball) which occurs specifically and uniquely in Graves’ disease. This forward protrusion of the eyes is due to immune mediated inflammation in the retro­orbital (eye socket) fat.

Measuring the level of thyroid-stimulating hormone (TSH) in the blood is usually all that is required.

A low TSH indicates that the pituitary gland is being inhibited by increased levels of T4 and/or T3 in the blood, and is therefore a reliable marker of hyperthyroidism.

Measuring specific antibodies, such as anti-TSH-receptor antibodies in Graves’ disease, or anti-thyroid-peroxidase in Hashimoto’s thyroiditis, may also contribute to the diagnosis.

Thyroid scintigraphy is a useful test to distinguish between causes of hyperthyroidism, and this entity from thyroiditis.

Ans: A. Start antithyroid drugs, and do urgent MRI brain

(Ref Harrison 19/e p2274. 18/e p2880; Sabiston 20/e p982, 19/e p1890; Schwartz 10/e p1533, 9/e p1541: Bailey 27/e p8 1 1, 26/e p614-616)

• Hyperthyroidism with elevated T4 and TSH levels and bitemporal hemianopia is highly suggestive of TSH-secreting adenoma.
• MRI – Confirm TSH-secreting pituitary adenoma diagnosis.

TSH producing macroadenomas:

• Rare.
• Often large & locally invasive.
• Along with thyroid goiter & hyperthyroidism, reflecting TSH overproduction.

Diagnosis:

• Elevated serum free T4 levels.
• Inappropriately normal or high TSH secretion.
• MRI – Evidence of pituitary adenoma.