Regarding Disorders Of The Thyroid Gland...

Regarding Disorders Of The Thyroid Gland answer the following questions...

1. What are the key features in a patient's history that are important in assessing for a possible functional thyroid disorder?
2. What are the important physical examination findings?
3. What laboratory data are used to confirm or refute the existence of a functional thyroid abnormality?

Answers And Discussion

1. What are the key features in a patient's history that are important in assessing for a possible functional thyroid disorder?
When assessing a patient's history for clues to a functional thyroid disease, it is important to keep in mind that thyroid hormones in general control metabolism. Therefore, when questioning patients about their medical history, it is important to ask specifically about elements related to metabolism.

For example, in the setting of hyperthyroidism,

• weight loss,
• anxiety, 
• tremor, 
• palpitations, 
• heat intolerance, 
• hyperdefecation, 
• insomnia,
• restlessness, and 
• changes in the hair or skin are important features. 

In contrast, in patients with suspected hypothyroidism, look for clues that indicate decreased metabolic activity. These include

• weight gain; 
• cold intolerance;
• constipation; 
• dry, scaly skin; 
• thick hair; 
• depression; 
• increased sleeping and fatigue; and 
• generalized lethargy.

2. What are the important physical examination findings?
Like the history, the physical examination should be performed to look for signs of hypermetabolism or hypometabolism.

In the setting of hyperthyroidism,

• a fast pulse; tremor; 
• sweating; 
• thin, soft, and velvety hair;
• very brisk reflexes; and 
• a hyperdynamic precordium are all features of increased metabolism. 

In addition, a very critical finding is an enlarged thyroid gland. If this is found in conjunction with a bruit, then the clinician can assume that the thyroid gland itself is overactive and overproducing thyroid hormone.

In contrast, the findings characteristic of hypothyroidism include

• pale, 
• sallow skin; 
• thick hair; 
• puffiness in the face and ankles; 
• cool extremities; 
• very delayed deep tendon relaxation; 
• bradycardia; and 
• a very quiet precordium. 

Again, an enlarged thyroid is an important physical examination finding. In this event, a firm, woody, or pebbly texture would indicate the presence of lymphocytic infiltration or Hashimoto's thyroiditis.

3. What laboratory data are used to confirm or refute the existence of a functional thyroid abnormality?
There is now a very sensitive and specific laboratory protocol to determine whether the patient has a functional thyroid disorder.
The first diagnostic test should be measurement of the serum TSH level using the sensitive TSH
assays. If this assay result proves to be within the normal range, then a functional abnormality of the thyroid has virtually been excluded. In contrast, an elevated TSH level means the thyroid gland is failing and the patient has primary thyroid gland failure, most commonly due to autoimmune thyroid
disease. Conversely, if the serum TSH level is low and undetectable, this indicates hyperthyroidism due to Graves' disease, a multinodular goiter, a hot nodule, excessive thyroid hormone ingestion, subacute thyroiditis, postpartum thyroiditis, or silent thyroiditis. If the TSH value is abnormal, then
thyroid hormone status should be assessed. This can be done either by obtaining a total T4 w ith a T3 resin uptake (to assess T4-binding globulin), or by simply ordering a free T4. Only in special circumstances is it necessary to test for total T3 or free T3 levels. Finally, in evaluating a patient with
suspected hyperthyroidism, if both the TSH level is low and the free T4 level is high, the next step is to perform a radioactive iodine uptake test and scan.
This test is very important in distinguishing causes of hyperthyroidism related to overproduction (i.e., Graves' disease, a multinodular goiter, or a hot nodule) from those related to excessive release but not production (i.e., subacute thyroiditis, postpartum thyroiditis, or silent thyroiditis), as well as
excessive thyroid hormone ingestion. The scan also infers the therapeutic approach. In the setting of strong clinical evidence for hypothyroidism with a low or normal TSH, it is also important to consider the relatively rare possibility of central, or secondary, hypothyroidism (defective TSH
production by the pituitary gland).