Type of test Blood

Normal findings

Test explanation and related physiology Thyroglobulin is the protein precursor of thyroid hormone and is made by both normal, well-differentiated, benign thyroid cells and thyroid cancer cells. Because thyroglobulin is normally only made by thyroid cells, it serves as a useful readout for the presence or absence of thyroid cells, especially after thyroid cancer surgery. This test is primarily used as a tumor marker for well differentiated thyroid cancers.

In the treatment of well-differentiated thyroid cancers, it is important to remove as much thyroid tissue as possible so that adjunctive radioactive iodine treatment will not go to residual thyroid gland tissue in the neck but will go instead to any meta static thyroid cells. If postoperative Tg levels are low, very little thyroid tissue remains. Tg can also be used as a tumor marker for thyroid cancer. Rising levels of Tg may indicate recurrence.

After thyroidectomy, thyroid hormone replacement is required for normal metabolic function. Thyroid-stimulating hormone (TSH) levels are usually very low when thyroid hormone is replaced adequately. Endogenous stimulation of any residual thyroid cells is minimal in these patients. As a result, Tg and endogenous thyroid hormones are low.

Thyrogen-stimulated testing has eliminated the need for withdrawal of thyroid hormone medications and provides a safe and effective method to elevate TSH levels so that even minimal levels of Tg can be detected. This allows patients to undergo periodic thyroid cancer follow-up evaluations while avoiding the often debilitating side effects of hypothyroidism, which is caused by withdrawal of hormone medication.

Thyrogen is a highly purified recombinant source of human TSH. Thyrogen raises serum TSH levels and thereby stimulates Tg production. Normal thyroid-remnant and well-differentiated thyroid tumors display a greater (> 10-fold) serum Tg response to TSH stimulation. If, after thyroid surgery, Thyrogen-stimulated Tg levels are elevated, either a significant amount of normal thy roid gland was left in the neck or metastatic disease exists.

Thyrogen stimulation is also used for patients undergoing I131 whole-body scanning for metastatic thyroid cancer. Now, with the use of Thyrogen, the ill effects of hormone withdrawal are not experienced.

Tg testing is complex because of the many techniques used for measurements. Also nearly 30% of thyroid cancer patients can have anti-Tg autoantibodies (TgAb) that interfere with Tg immunoassays (most commonly false negatives). As a result TgAb testing should performed with Tg testing.

In patients with thyroid cancer an aspirate from a cervical lymph node can be tested for the presence of thyroglobulin if there is suspicion that thyroid cancer has spread to the lymphatic system.

Interfering factors

 • Tg levels are decreased in less well-differentiated thyroid cancers.

• Thyrogen stimulation of Tg levels is less in patients whose tumors do not have TSH receptors or whose tumors cannot make Tg.

• Tg autoantibodies cause either underestimation or over estimation of serum Tg measurements made by immunometric assay (IMA) or radioimmunoassay (RIA) methods, respectively.

 Procedure and patient care

• See inside front cover for Routine Blood Testing.

 • Fasting: no

• Blood tube commonly used: serum separator

 • Determine whether the patient is to have a whole-body nuclear scan along with the Tg blood test.

• If Thyrogen stimulation is to be used:

1. Administer Thyrogen intramuscularly to the buttock every 24 hours for two or three doses as ordered.

2. Collect a venous blood sample in a gold-top (serum separator) tube after 3 days.

 • For radioiodine imaging: 1. The nuclear medicine technologist will administer the radioiodine 24 hours after the final Thyrogen injection.

2. Scanning is usually performed 48 hours after radioiodine administration. Whole-body images are acquired for a minimum of 30 minutes and/or should contain a mini mum of 140,000 counts.

 3. Scanning times for single (spot) images of body regions may be obtained.

 Abnormal findings

 Increased levels

- Residual thyroid tissue in the neck

- Metastatic thyroid cancer

اخر الاخبار

اخبار العتبة العباسية المقدسة

مستشفى الكفيل يدخل قائمة الاعتماد الدولية بجودة الخدمة وسلامة المرضى

جامعة العميد تقيم ورشة عمل تدريبية في مجال التعليم الطبي الحديث

سماحة السيد الصافي يدعو إلى الاستمرار في تحقيق تراث العلماء الأعلام وتسليط الضوء على فكرهم

شعبة الخطابة الحسينية تختتم الموسم الثامن من مشروع الدورات الصيفية في كربلاء

المزيد

الآخبار الصحية

الأطعمة الحارة.. "سر صغير" يغير صحة قلبك وعقلك

وباء صامت.. الملايين حول العالم مصابون بالسكري دون أن يعلموا !

لماذا ينصح بتناول تفاحة يوميا؟

8 فواكه طبيعية تمنحك نوما هنيئا.. وتخلصك من الأرق

المزيد

الآخبار التكنلوجية

ثلاث علامات على وجود مشاكل خطيرة في محرك السيارة ؟

ماذا نعرف عن اللقاح الروسي ضد السرطان؟

مركبة فضاء تعثر على دليل عن وجود حياة قديمة على المريخ

لتدريب الذكاء الاصطناعي.. الصين تخطط لإنشاء شبكة حوسبة موحدة

المزيد

مواضيع ذات صلة

thyroid-stimulating hormone (TSH, Thyrotropin, TRH stimulation test)

thrombosis indicators

Laboratory Investigations of Growth Hormone

Growth Hormone Deficiency

Laboratory Diagnosis of Thrombophilia

thromboelastography (Thromboelastometry)

throat and nose cultures

testosterone (Dihydrotestosterone [DHT])

Biomarkers of Stroke

Soluble IL-33 Receptor (sST2)

syphilis detection test (Serologic test for syphilis [STS], Venereal Disease Research Laboratory [VDRL], Rapid plasma reagin [RPR], Fluorescent treponemal antibody test [FTA])

sweat test (Sweat electrolyte test, Sweat chloride test, Sweat conductivity test, Iontophoretic sweat test)