Thyroid (5)

Symptoms of hypothyroidism include:
• Fatigue, loss of energy, lethargy
• Weight gain
• Decreased appetite
• Cold intolerance
• Dry skin
• Constipation
• Menstrual disturbances, impaired fertility
• Hair loss
• Sleepiness
• Muscle pain, joint pain, weakness in the extremities
• Depression
• Emotional lability, mental impairment
• Forgetfulness, impaired memory, inability to concentrate
• Decreased perspiration
• Paresthesias, nerve entrapment syndromes
• Blurred vision
• Decreased hearing
• Fullness in the throat, hoarseness

Physical signs of hypothyroidism include the following:
• Weight gain
• Slowed speech and movements
• Dry skin
• Jaundice
• Pallor
• Coarse, brittle, straw-like hair
• Loss of scalp hair, axillary hair, pubic hair, or a combination
• Dull facial expression
• Coarse facial features
• Periorbital puffiness
• Macroglossia
• Goiter (simple or nodular)
• Hoarseness
• Decreased systolic blood pressure and increased diastolic blood pressure
• Bradycardia
• Pericardial effusion
• Nonpitting edema (myxedema)
• Pitting edema of lower extremities
• Hyporeflexia with delayed relaxation, ataxia, or both

Thyroid carcinoma most commonly manifests as a painless, palpable, solitary thyroid nodule. Malignant thyroid nodules are usually painless. Sudden onset of pain is more strongly associated with benign disease, such as hemorrhage into a benign cyst or subacute viral thyroiditis, than with malignancy.

Solitary thyroid nodules can vary from soft to hard. Hard and fixed nodules are more suggestive of malignancy compared with supple mobile nodules. Thyroid carcinoma is usually nontender to palpation. Firm cervical masses are highly suggestive of regional lymph node metastases. Vocal fold paralysis implies involvement of the recurrent laryngeal nerve.

Palpable thyroid nodules are present in approximately 5% of the general population, and most represent benign disease. Palpable and nonpalpable nodules of similar size have the same risk for malignancy.

The patient's age at presentation is important because solitary nodules are most likely to be malignant in patients older than 60 years and in patients younger than 30 years. In addition, thyroid nodules are associated with an increased rate of malignancy in males. Growth of a nodule may suggest malignancy. Rapid growth is an ominous sign.

Hashimoto thyroiditis is a histologic diagnosis. Typically, the thyroid gland shows diffuse lymphocytic and plasma cell infiltration with formation of lymphoid follicles from follicular hyperplasia and damage to the follicular basement membrane. Atrophy of the thyroid parenchyma is usually evident. Correlation with the presence of thyroid autoantibodies, namely anti-TPO and antithyroglobulin (anti-Tg), is helpful in confirming the diagnosis.

Iodine uptake and scan are usually not indicated for the diagnosis of Hashimoto thyroiditis. The usefulness of radioactive iodine and scan is in classifying a nodule as either hot or cold. A cold thyroid nodule indicates a higher risk for malignancy and therefore a need for fine-needle aspiration.

The treatment of choice for Hashimoto thyroiditis (or hypothyroidism from any cause) is thyroid hormone replacement. The drug of choice is orally administered levothyroxine sodium, usually for life. Tailor and titrate the dose of levothyroxine sodium to meet the individual patient's requirements. The goal of therapy is to restore a clinically and biochemically euthyroid state. The standard dose is 1.6-1.8 µg/kg lean body weight per day, but the dose is patient dependent. The free T4 and TSH levels are within reference ranges in the biochemically euthyroid state, with the TSH level in the lower half of the reference range.

Patients younger than 50 years who have no history or evidence of cardiac disease can usually be started on full replacement doses. Start patients older than age 50 years and younger patients with cardiac disease on a low dose of 25 µg (0.025 mg) per day, with clinical and biochemical reevaluation in 6-8 weeks. Carefully titrate the dose upward to achieve a clinical and biochemical euthyroid state.

For more on Hashimoto thyroiditis, read here.

The most reliable screening measure of thyroid function is the TSH level. TSH levels usually are suppressed to unmeasurable levels (
A significant number of healthy people without active thyroid disease have mildly positive anti-TPO antibody titers; thus, the test should not be performed for screening purposes.

The following are RAIU (over neck) findings associated with various forms of thyrotoxicosis and hyperthyroidism:

• Diffuse toxic goiter (Graves’ disease) - Increased (moderate to high: 40%-100%)

• Toxic multinodular goiter (Plummer disease) - Increased (mild to moderate: 25%-60%)

• Thyrotoxic phase of subacute thyroiditis - Decreased (very low:
• Toxic adenoma - Increased (mild to moderate: 25%-60%)

Radioactive iodine therapy for Graves’ disease is a risk factor for Graves ophthalmopathy.

Thyroidectomy is not the recommended first-line therapy for hyperthyroid Graves’ disease. Surgery is a safe alternative therapeutic option in patients who are not compliant with or cannot tolerate antithyroid drugs, have moderate to severe ophthalmopathy, have large goiters, or refuse or cannot undergo radioiodine therapy.

The most commonly used therapy for Graves’ disease is radioactive iodine. Indications for radioactive iodine over antithyroid agents include a large thyroid gland, multiple symptoms of thyrotoxicosis, high levels of thyroxine, and high titers of thyroid-stimulating immunoglobulins (TSI).

Patients currently taking antithyroid drugs must discontinue the medication at least 2 days prior to taking the radiopharmaceutical. If thyroid function does not normalize within 6-12 months of radioactive iodine treatment, a second course at a similar or higher dose can be given. Third courses are rarely needed.