SUMMARY: Introduction and objective: The aggressive histological subtypes of thyroid cancer are less common and have a worse prognosis than well -differentiated ones (DTC). The most important aggressive subtypes are Hürtle cell carcinoma (CHH), anaplasic and poorly differentiated carcinoma. In this review, we are going to evaluate the role of PET-CT, especially with 18F-FDG, in these aggressive histological lines, as well as in aggressive subtypes of DTC (tall cells, diffuse sclerosing…) and in radioiodine-refractory differentiated thyroid carcinoma. Synthesis: Although the main indication for 18F-FDG PET in thyroid cancer is suspected recurrence, in patients with DTC with elevated serum thyroglobulin and radioiodine-negative whole-body scan (WBS), this technique has increasing applications in DTC. Likewise, 18F-FDG PET is also an efficient diagnostic tool in the study of anaplastic carcinoma, poorly differentiated and other aggressive lines. It is recommended, in current clinical guidelines, as part of the initial staging in anaplastic, poorly differentiated, and invasive HCC. And it is increasingly used in other indications such as prognostic assessment, evaluation of treatment response, and even during the follow-up of high-risk patients. The use of other PET tracers, such as 68Ga-PSMA and 68Ga-DOTATATE have not clearly demonstrated their clinical benefit over 18F-FDG. They are usually limited to cases in which it is necessary to assess the density of somatostatin analogs and PSMA receptors prior to metabolic therapy. Conclusions: 18F-FDG PET-CT is the most effective functional diagnostic technique in the study of poorly differentiated and aggressive thyroid neoplasms, since they show little or no avidity for radioiodine and however high affinity for 18F-FDG. The role of other PET tracers for the evaluation of these tumors is promising, although it still needs studies with a larger number of patients.

RESUMEN: Introducción y objetivo: Los subtipos histológicos agresivos de cáncer de tiroides son menos frecuentes y tienen peor pronóstico que los bien diferenciados (CDT). Los subtipos agresivos más importantes son el carcinoma de células de Hürthle (CCH), el carcinoma anaplásico y el pobremente diferenciado. En esta revisión vamos a hablar del papel del PET-CT, especialmente con 18F-FDG, en estas estirpes histológicas agresivas, así como en subtipos agresivos de CDT (células altas, esclerosante difuso…) y en el carcinoma de tiroides refractario al radioyodo. Síntesis: Aunque la principal indicación del PET con 18F-FDG en el cáncer de tiroides es la sospecha de recidiva, en pacientes con CDT con tiroglobulina sérica elevada y rastreo corporal total (RCT) con radioyodo negativo, esta técnica tiene crecientes aplicaciones en el CDT. Así mismo, el PET con 18F-FDG también es una herramienta diagnóstica eficiente en el estudio del carcinoma anaplásico, el pobremente diferenciado y otras estirpes histológicas agresivas. Es recomendado en las guías clínicas actuales como parte de la estadificación inicial en cánceres de tiroides anaplásico, pobremente diferenciados y CCH invasivo. Y cada vez se emplea más en otras indicaciones como valoración pronóstica, de la respuesta al tratamiento, e incluso durante el seguimiento de pacientes de alto riesgo. El empleo de otros trazadores para PET como el 68Ga-PSMA y el 68Ga-DOTATATE no han demostrado claramente su beneficio clínico frente a la 18F-FDG. Suelen limitarse a casos en los que sea necesaria la valoración de la densidad de receptores de análogos de somatostatina y PSMA previa a terapia metabólica. Conclusiones: El PET-CT con 18F-FDG es la técnica diagnóstica funcional más efectiva en el estudio de las neoplasias tiroideas poco diferenciadas y agresivas, ya que muestran escasa o nula avidez por el radioyodo y sin embargo elevada afinidad por la 18F-FDG. El papel de otros trazadores PET para la valoración de estos tumores es prometedor, aunque aún necesita de estudios con mayor número de pacientes.

ABSTRACT The objective of this research was to evaluate a possible corrective measure against negative metabolic states, as occurs in the advanced stage of gestation in ewes, and that sometimes produces a disease called pregnancy toxaemia. In the present research, we found that the joint administration of i.v. lysine-vasopressin (0.08 IU/kg body weight, BW) and an oral glucose solution (50 g) produces an increase in blood glucose, which persists for some time (up to 6 h); therefore, it could be used in the treatment of pregnancy toxaemia. This therapy is based on the fact that lysine-vasopressin induces gastric groove closure in adult ruminants, enabling orally administered glucose to reach the abomasum directly, from where it rapidly passes into the intestine and is immediately absorbed. We can say that the tested treatment causes a significant increase in blood glucose in ewes affected by toxaemia caused by fasting, which, although less marked than conventional therapy with intravenous drip glucose, remains longer, regularizing other parameters indicative of energy metabolism in fasting ewes.