Thyroid Stimulating Hormone (TSH)
CPT Code(s):
84443
Turnaround Time:
4 hours
Specimen Requirements
Preferred Specimen:
Serum
Minimum Volume:
1.0 mL
Transport Container:
Serum Separator Tube (SST) or Red Top Tube
Transport Temperature:
Room Temperature
Collection Instructions:
Allow blood to clot completely prior to centrifugation. Separate serum from cells within 45 minutes of collection.
Rejection Criteria:
Citrate, Fluoride,Sodium Heparin specimen; gross hemolysis; lipemia; improper labeling
Stability Criteria
Room Temperature:
8 days
Refrigerated:
14 days
Frozen:
30 days
Clinical Significance
The Thyroid-Stimulating Hormone (TSH) test has specific clinical significance and diagnostic use in assessing thyroid function and diagnosing thyroid disorders. Here are some key points regarding its clinical significance:
1. Thyroid Function Assessment: TSH is produced by the pituitary gland and regulates the production of thyroid hormones (T3 and T4) by the thyroid gland. TSH measures the level of TSH in the blood and serves as the primary screening tool to evaluate thyroid function.
2. Hypothyroidism Diagnosis: Elevated TSH levels are the hallmark of primary hypothyroidism, a condition where the thyroid gland fails to produce sufficient thyroid hormones. TSH levels increase to stimulate the thyroid gland to produce more hormones. A high TSH level, combined with low levels of T3 and T4, confirms the diagnosis of hypothyroidism.
3. Hyperthyroidism Diagnosis: In cases of primary hyperthyroidism, where the thyroid gland produces excessive thyroid hormones, TSH levels are typically suppressed. A low or undetectable TSH level, along with elevated T3 and T4 levels, supports the diagnosis of hyperthyroidism.
4. Subclinical Thyroid Dysfunction: Subclinical hypothyroidism and subclinical hyperthyroidism are conditions where TSH levels are outside the normal range, but T3 and T4 levels remain within the normal range. These conditions may have subtle symptoms or no symptoms at all but can increase the risk of developing overt thyroid dysfunction. TSH testing helps identify these individuals who may benefit from close monitoring or treatment intervention.
5. Monitoring Thyroid Replacement Therapy: Patients receiving thyroid hormone replacement therapy, such as those with hypothyroidism, require regular TSH testing to ensure their thyroid hormone levels are within the therapeutic range. TSH levels are used to guide medication adjustments and maintain optimal thyroid function.
6. Screening Newborns: TSH testing is routinely performed as part of newborn screening programs to detect congenital hypothyroidism. Early detection and treatment of congenital hypothyroidism are crucial to prevent complications and ensure normal development.
7. Evaluating Pituitary Function: TSH testing can help assess pituitary function. Abnormal TSH levels may indicate pituitary disorders or dysfunction in the hypothalamus-pituitary-thyroid axis.
In summary, TSH is clinically significant in evaluating thyroid function, diagnosing hypothyroidism and hyperthyroidism, detecting subclinical thyroid dysfunction, monitoring thyroid replacement therapy, screening newborns for congenital hypothyroidism, and assessing pituitary function. It plays a crucial role in identifying thyroid disorders, guiding treatment decisions, and ensuring optimal thyroid hormone balance for overall health and well-being.