Thyroglobulin and lactic dehydrogenase isozymes in cystic fluid of thyroid nodules

Alterations in serum thyroid-related constituents after thyroid fine-needle biopsy: a systematic review

BACKGROUND

Thyroid fine-needle biopsy (FNB) is a simple, reliable, inexpensive, and generally safe diagnostic procedure in the management of thyroid nodules. Local pain and minor hematomas are the most common clinical complications, and hemorrhage and fibrosis the most common histological alterations after thyroid FNB. FNB can also trigger biochemical alterations in serum, since it may destroy thyroid follicles. In this review we summarized the biochemical alterations in serum that occur after diagnostic thyroid FNB, aiming to review information that would be potentially useful in interpreting thyroid tests in patients who recently had a thyroid FNB.

SUMMARY

Computerized advanced search for primary evidence was performed in the PubMed (Public/Publisher MEDLINE) electronic database not limited by publication time and English language. An increase in serum thyroglobulin (Tg) ranging from 35% to 341% occurs in 33-88% of patients subjected to FNB. Serum Tg concentrations typically return to baseline about 2-3 weeks after FNB. The abrupt release of Tg after FNB may induce the production of autoantibodies to Tg and thyroid hormones in a minority of patients. There is little information on the effect of FNB on autoantibodies to thyroid peroxidase. No changes seem to occur in thyroid-stimulating hormone, total thyroxine, free thyroxine, free triiodothyronine (T3), or reverse T3, while controversy exists for T3.

CONCLUSIONS

The degree of increase in serum Tg after FNB is highly variable and not a predictor of whether the biopsied nodule is benign or malignant. The increase or development of Tg autoantibodies that occurs in some patients does not appear to be of clinical significance. Development of autoantibodies to thyroid hormones may be more likely in patients whose biopsied nodule is benign than malignant, but further studies are required to confirm this. If changes in serum thyroid-stimulating hormone or thyroid hormones are noted in a patient with a history of a recent fine-needle aspiration, they should be investigated since they are not likely to be related to the biopsy.

Biochemical and hormonal composition, cytological examination of thyroid cyst fluid, and comparison according to gender and color of cyst fluid

BACKGROUND

The aim of this study was to evaluate the biochemical composition and cytological examination of 25 thyroid cyst fluid specimens that were obtained by fine needle aspiration, and to compare results according to gender and color of cyst fluid. We anticipated that measuring biochemical routine parameters in cyst fluid would contribute to the pathophysiology of thyroid nodule formation leading to better clinical outcomes when compared to therapies based only on cytological examination.

METHODS

We analyzed 23 parameters in serum and cyst fluid samples taken from 25 euthyroid patients. In addition, cytological examination of cyst fluids was performed.

RESULTS

We revealed that mean levels of glucose, phosphorus, high-density lipoprotein cholesterol, antibodies to thyroglobulin, and activities of alanine aminotransferase and alkaline phosphatase were lower, and mean levels of uric acid, free triiodothyronine, free thyroxine, and thyroglobulin and activity of lactate dehydrogenase in the cyst fluid of thyroid nodules were higher when compared to their own serum sample levels. Also, there were significant differences according to gender and color of cyst fluid.

CONCLUSIONS

Biochemical examination of thyroid cyst fluid may be of value for the clinician to evaluate the nature of thyroid nodules. The potential benefits of thyroid cyst fluid examination warrant further investigation in patients with thyroid nodules.

Thyroglobulin and human thyroid cancer

Thyroglobulin (Tg) is a large molecule containing 2750 amino acids with a molecular weight of 330 kD and twenty putative N-linked glycosylation sites. Tg gene expression is regulated by thyroid transcription factor 1 (TTF-1) and human paired box 8 (Pax-8). Iodinated Tg is stored in the lumen of the thyroid follicles and is released in response to specific hormonal stimulation by thyroid stimulating hormone (TSH). Following Tg reabsorption by thyrocytes and subsequent degradation, thyroid hormones triiodothryronine (T(3)) and thyroxine (T(4)) are secreted in the bloodstream. Mutations within the Tg gene cause defective thyroid hormone synthesis, resulting in congenital hypothyroidism. Thyroid carcinoma may develop from dyshormonogenic goiters due to Tg mutation. Post-thyroidectomy Tg levels are apparently associated with prognosis of papillary and follicular thyroid carcinomas and may predict tumor recurrence and metastastic potential. The detection of Tg by biochemical and molecular means has important diagnostic significance due to its pleiotropic roles in identification of tissue of thyroid origin, differentiation, and post-operative follow-up.

Management of simple nodular goiter: current status and future perspectives

The simple nodular goiter, the etiology of which is multifactorial, encompasses the spectrum from the incidental asymptomatic small solitary nodule to the large intrathoracic goiter, causing pressure symptoms as well as cosmetic complaints. Its management is still the cause of considerable controversy. The mainstay in the diagnostic evaluation is related to functional and morphological characterization with serum TSH and (some kind of) imaging. Because malignancy is just as common in patients with a multinodular goiter as patients with a solitary nodule, we support the increasing use of fine-needle aspiration biopsy (cytology). Most patients need no treatment after malignancy is ruled out. In case of cosmetic or pressure symptoms, the choice in multinodular goiter stands between surgery, which is still the first choice, and radioiodine if uptake is adequate. In addition to surgery, the solitary nodule, whether hot or cold, can be treated with percutaneous ethanol injection therapy. If hot, radioiodine is the therapy of choice. Randomized studies are scarce, and the side effects of nonsurgical therapy are coming into focus. Therefore, the use of the optimum option in the individual patient cannot at present be based on evidence. However, we are of the view that levothyroxine, although widely used, should no longer be recommended routinely for this condition. Within a few years, the introduction of recombinant human TSH and laser therapy may profoundly alter the nonsurgical treatment of simple nodular goiter.

Serum thyroglobulin measurement. Utility in clinical practice

Serum thyroglobulin measurement has greatly facilitated the clinical management of patients with differentiated thyroid cancer and a variety of other thyroid disorders. Thyroglobulin autoantibodies remain a significant obstacle to the clinical use of thyroglobulin measurement. The interpretation of any given thyroglobulin value requires the careful synthesis of all pertinent clinical and laboratory data available to the clinician. The diagnostic use of rhTSH-stimulated thyroglobulin levels has greatly facilitated the follow-up of low-risk patients with thyroid cancer. Although the measurement of thyroglobulin mRNA from peripheral blood is likely to affect the future management of these patients, it is expected that serum thyroglobulin measurement will continue to have a principal role in the care of patients with differentiated thyroid cancer.