Thyroid ultrasound: beyond the diagnosis of thyroid nodules

Abstract

I n this issue of the Archives of Endocrinology and Metabolism, there are two articles in which thyroid ultrasound was used to clarify some physiopathological aspects of the thyroid, evidencing the notable usefulness of this method beyond its routine use in the diagnosis of nodules and thyroiditis.The first article, "Should human chorionic gonadotropine treatment increase thyroid volume?", by Ayten Oguz and cols. from the Sutcu Iman University in Kahramanmaras, Turkey, presents a very interesting and pioneering observation showing that the administration of human chorionic (hCG) in the treatment of isolate hypogonadotropic hypogonadism (IHH) in men induced increased thyroid volume (1).This original observation confirms classical endocrinological evidence on the crossreactivity between hCG and TSH. Both substances are glycoprotein hormones with structural similarity and whose thyrotrophic activities have been known for a long time (2). TSH and hCG are made up by two subunits (alpha and beta), that are linked to each other, forming active heterodimeric structures; the alpha subunit of both compounds is identical, but the beta subunits also show high structural homology. Similarly, TSH receptors show structural homology with LH/CG receptors, which are bound to protein G (3). Thus, hCG thyrotrophic activity may be explained by either the structural homology between hCG and TSH or between the LH/CG and TSH receptors. Therefore, hCG is able to bind to TSH receptors of thyroid follicular cells and activate intracellular messengers, such as cyclic AMP, and induces growth of follicular cells in culture (3).In normal pregnancy, when hCG is high, TSH decreases, mirroring the hCG peak (3,4); besides, women with hyperemesis gravidarum show high levels of hCG, which cause transitory thyrotoxicosis (4). Finally, it is know that several pathological conditions, such as hydatidiform moles, choriocarcioma, and other types of cancer that are characterized by high levels of hCG and may induce thyrotoxicosis, which disappears after the tumor is removed (3).In fact, hCG behaves as a "weak" thyroid stimulator; it is estimated that a 10,000 IU/liter increase in circulating hCG corresponds to a 0.6 pmol/L (0.1 ng/dL) elevation in T4, leading to a TSH decrease of 0.1 mU/L (3). Besides, for clinical hyperthyroidism to ensue, a patient has to show prolonged elevation of hCG levels (4).Oguz and cols. treated 44 men (18 to 54 years old) carriers of IHH with testosterone (n = 19) or hCG (n = 25) for about 6 months, and compared them with a matched healthy control group, evaluating thyroid function and volume. They did not mention the doses of testosterone or hCG that were employed.Individuals treated with hCG showed, after 6 months, higher serum levels of testosterone and increased T4 (from 1.16 ± 0.19 ng/dL to 1.34 ± 0.49 ng/dL, p = 0.024) and thyroid volume (from 8.76 ± 1.13 mL to 9.02 ± 0.99 mL, p = 0.001).

Role of High Frequency Ultra-Sonogram & Color Duplex Findings with FNAC in Identifying Benign and Malignant Thyroid Nodule

“…All patients with thyroid swelling were assessed by using high frequency Ultra-sonogram as initial step [6] . Ultra-sonogram investigation can assess both palpable and non-palpable thyroid swellings, if present [7] . We can take the advantage of US for guiding FNAC biopsy for HPE correlation of both palpable and non-palpable thyroid nodules [8] .…”