General medicine parte 1

TREATMENT

In most patients, hypothyroidism is a permanent condition requiring lifelong treatment. Therapy consists of thyroid hormone replacement, unless the hypothyroidism is transient (as after painless thyroiditis or subacute thyroiditis) or reversible (due to a drug that can be discontinued).

The primary goal of therapy is restoration of the euthyroid state, which can be readily accomplished in almost all patients by oral administration of synthetic thyroxine (T4, levothyroxine).

Appropriate treatment reverses all the clinical manifestations of hypothyroidism.

Goals of therapy

The goals of therapy are:

• Amelioration of symptoms
• Normalization of serum TSH secretion
• Reduction in the size of goiter (if present)
• Avoidance of overtreatment (iatrogenic thyrotoxicosis)

Treatment is aimed to keep serum TSH within the normal reference range approximately 0.5 to (5.0 mU/L). However, it is important to note that there is an age-related shift towards higher TSH concentrations in older patients, with an

The upper limit of normal of approximately 7.5 mU/L in 80-year-olds. Among patients with goiter, approximately 50% will have some decrease in goiter size, which lags behind the fall in TSH secretion.

THYROID NODULES

Thyroid nodules come to clinical attention when noted:

• By the patient
• By a clinician during:
• Routine physical examination
• A radiologic procedure, such as carotid ultrasonography, neck or chest computed tomography (CT), or positron emission tomography (PET) scanning

Their clinical importance is primarily related to the need to exclude thyroid cancer, which accounts for 4 to 6.5 percent of all thyroid nodules in nonsurgical series.

EVALUATION

Several different disorders can cause thyroid nodules. The clinical importance of the thyroid nodule evaluation is primarily related to the need to exclude thyroid cancer, which is present in 4% to 6.5% of thyroid nodules. The prevalence of cancer is higher in several groups:

• Children
• Adults less than 30 years of age
• Patients with a

History of Head and Neck Irradiation

Patients with a family history of thyroid cancer

Serum TSH

Thyroid function should be assessed in all patients with thyroid nodules.

Serum TSH is an independent risk factor for predicting malignancy in a thyroid nodule (increasing risk for higher TSH values)

Thyroid ultrasonography

Thyroid ultrasound should be performed in all patients with a suspected thyroid nodule or nodular goiter on physical examination or with nodules incidentally noted on other imaging studies (carotid ultrasound, CT, MRI, or udeoxyglucose [FDG]- PET scan)

- Provides more information than physical examination: thyroid ultrasonography is used to answer questions about the size and anatomy of the thyroid gland and adjacent structures in the neck. It provides considerably more anatomic detail than thyroid scintigraphy, CT, and physical examination

- Helps select nodules for ne-needle aspiration (FNA): there are several ultrasonographic findings that are suspicious for thyroid cancer. The

The predictive value of these characteristics varies widely, and we do not rely on thyroid ultrasound to diagnose cancer or to select patients for surgery. However, ultrasound findings can be used to select nodules for FNA biopsy.

Subsequent evaluation is based upon the TSH level and sonographic features of the nodule(s).

If the serum TSH concentration is subnormal, indicating overt or subclinical hyperthyroidism, the possibility that the nodule is hyperfunctioning is increased and thyroid scintigraphy should be performed next.

Thyroid hormone production from some autonomous nodules (especially smaller nodules) may suppress TSH only within the lower portion of the normal range (eg, <1 mU/L). Scintigraphy may be informative in such patients, especially if prior TSH levels were subnormal, or when the results of an FNA suggest a follicular neoplasm.

Thyroid scintigraphy is used to determine the functional status of a nodule. A subnormal

Serum TSH, indicating overt or subclinical hyperthyroidism, increases the possibility that a thyroid nodule is hyperfunctioning. Since hyperfunctioning nodules rarely are cancer, a nodule that is hyperfunctioning on radioiodine imaging does not require FNA.

In addition, thyroid scintigraphy may be useful in patients with multiple thyroid nodules to select those that are hypofunctional and therefore may require FNA.

Radionuclide scanning is contraindicated during pregnancy. If a woman is breastfeeding, breastfeeding should be held if a radionuclide scan is obtained. The amount of time will depend on which isotope is used (breastfeeding needs to be held longer if radioiodine is used).

Scintigraphy utilizes one of the radioisotopes of iodine (usually 123-I) or technetium-99m pertechnetate (radioiodine scanning is preferred). These radioisotopes are handled differently by thyroid follicular cells. Normal thyroid follicular cells take up both technetium and radioiodine, but only radioiodine is organi ed.

hyperfunctioning.Autonomous nodules that do not make sufficient thyroid hormone to suppress serum TSH concentrations will appear indeterminate on thyroid scintigraphy. Autonomous nodules account for only 5 to 10 percent of palpable nodules. Only a few patients with autonomous nodules have been found to have thyroid cancer, and only a few of these cancers were aggressive. Furthermore, in some of these patients, the cancer was adjacent to the autonomous nodule rather than within it. Since hyperfunctioning nodules rarely are cancer, a nodule that is hyperfunctioning on radioiodine imaging does not require FNA 20fi fi fi ff ffi fi3.

Indeterminate

Because scintigraphy is two dimensional, its limitations result from the superimposition of abnormal nodular tissue and normally functioning thyroid tissue. Thus, while over 80 percent of nonautonomous nodules greater than 2 cm appear cold, smaller nodules present as a filling defect in less than one-third of cases. The remaining majority of smaller nodules are

indeterminate on thyroid scintigraphy. They could represent either small, nonfunctioning nodules anterior or posterior to normally functioning thyroid tissue, or autonomous nodules that do not produce sufficient thyroid hormone to suppress TSH. These indeterminate nodules should not be referred to as warm or functioning, since the majority are, in fact, nonfunctioning nodules.

Indeterminate nodules on scintigraphy should be evaluated by FNA if they meet sonographic criteria for sampling.

TSH NORMAL OR ELEVATED

If the serum TSH concentration is normal or elevated and the nodule meets sonographic criteria for sampling, the next step in the evaluation of a thyroid nodule is a palpation or ultrasound-guided FNA biopsy.

FNA biopsy is the most accurate method for evaluating thyroid nodules and identifying patients who require surgical resection.

FNA biopsy has resulted in improved diagnostic accuracy, a higher malignancy yield at the time of surgery, and significant cost reductions.

Nodules that do not meet

Fine-needle aspiration biopsy

The presence of suspicious ultrasound features is more predictive of malignancy than nodule size alone.

A decision analysis of thyroid nodule biopsy criteria favors the approach of selecting nodules with suspicious ultrasonographic characteristics for biopsy over the approach of biopsy for all nodules ≥1 cm.

FNA should be performed in any nodule (regardless of size) with the following suspicious sonographic features:

• Subcapsular locations adjacent to the recurrent laryngeal nerve or trachea
• Extrathyroidal extension
• Extrusion through rim calcifications
• Associated with sonographically abnormal cervical lymph nodes

Thyroid nodules under 5 mm are technically difficult to biopsy; before considering such a biopsy, the risk of a nondiagnostic result and the reliability of a negative result should be discussed with the patient. In the presence of abnormal cervical lymph nodes, FNA cytology may be

• Irregular margins
• Microcalci cations
• Taller than wide shape
• Rim calci cations with extrusion of soft tissue