Inhibidores de tirosina cinasa y disfunción tiroidea / Tyrosine kinase inhibitors and thyroid dysfunction

Los inhibidores de la tirosina cinasa son utilizados para el tratamiento de diversas neoplasias interfiriendo en múltiples vías de proliferación celular y angiogénesis tumoral. Estos fármacos presentan efectos adversos de clase, destacándose entre ellos la afectación de la función tiroidea. Existen diferentes mecanismos propuestos por los cuales estos agentes orales llevan tanto al hipotiroidismo como a la tirotoxicosis. Aún no existe consenso sobre el seguimiento y tratamiento ante la aparición de estos efectos.

Tyrosine kinase inhibitors are used for the treatment of different types of tumours, interfering in various cell proliferation pathways, and tumour angiogenesis. These oral agents have side effects, thyroid dysfunction outstanding among them. There are different mechanisms through which these agents lead to hypothyroidism, as well as thyrotoxicosis. There is still no consensus on the treatment and follow-up of the above mentioned effects.

Male-female differences in 6-sulfatoxymelatonin excretion in hypopituitary patients

ABSTRACT Objective To evaluate melatonin secretion in adult hypopituitary patients with Growth Hormone deficiency (AGHD) on and off replacement therapy. Subjects and methods We studied 48 subjects: 12 (6 males) untreated AGHD (AGHDnt), 20 (10 males) treated AGHD (AGHDt) and 16 healthy subjects (8 males) as control group (CG). We measured urinary 6-sulfatoxymelatonin (6-SM) in total (24 h samples), nocturnal (6-SMn): 1800-0800 and diurnal samples (6-SMd): 0800-1800. Results Significant differences were observed among the 3 groups of male subjects, in total 6-SM (p < 0.05), nocturnal 6-SM (p < 0.02) and nighttime-daytime delta values (p < 0.003). CG had significantly higher values than the AGHDnt in total 6-SM (p < 0.01), nocturnal 6-SM (p < 0.05) and nighttime-daytime delta values (p < 0.01). AGHDt patients showed significantly higher levels in nighttime-daytime delta values than AGHDnt patients (p < 0.05). In females, no significant differences were found among the 3 groups studied in total, nocturnal, diurnal or nighttime-daytime delta values. In males, significant correlations were found among total 6-SM (r = 0.58; p = 0.029), nocturnal 6-SM (r = 0.70; p = 0.006) and nighttime-daytime delta values (r = 0.71; p = 0.004) vs. serum IGF-1 levels in subjects evaluated. In females, significant correlations were found among total 6-SM (r = 0.57; p = 0.02) vs. serum IGF-1 levels in subjects evaluated. A tendency towards a significant correlation was found in diurnal 6-SM (r = 0.48; p = 0.07). Conclusions Our findings show a sexual dimorphism in 6-SM excretion in AGHD patients and provide an interesting approach to a further understanding of some chronobiological disorders involved in GH deficiency.

Reproducibility and variability of the arginine test in normal adults: comparison between sexes

The biochemical diagnosis of growth hormone deficiency in adults (AGHD) remains controversial, mainly as regards stimulation tests and suggested cut-off lines. The insulin tolerance test proved to be the most effective growth hormone (GH) secretagogue in normal males, but a poor intra-individual reproducibility has been reported. Given the safety of the arginine (AST), we decided to evaluate the incidence of false negatives (non responder normal subjects), its reproducibility and variability. Twenty five healthy non-obese volunteers (16 males, 9 females) with a chronological age range between 19 and 40 years, (mean: 29.8) were evaluated. AST was performed (0.5 g/kg IV infusion for 30 min), measuring GH (IRMA) at baseline (B), 30, 60 and 90 minutes, and it was repeated in the same subject 7 to 30 days later; in females both tests were performed in the early follicular phase. Results (median and range) were: 1st test B: 0.61 (0.35-22.60) mug/L; maximal response (Mx Resp) 10.00 (0.48-48.80 mug/L 2nd test B:0.50 (0.38-27.0) mug/L; Mx Resp 11.00 (0.50-47.70) mug/L. The statistical evaluation (Wilcoxon signed rank test) showed no differences between B vs. B and Mx Resp vs Mx Resp. Separated by Sex, males showed: 1st test: B 0.45 (0.35-4.30) mug/L; Mx Resp 6.30 (0.48-48.80) mug/L. 2nd test B 0.46 (0.38-8.80) mug/L; Mx Resp 10.90 (0.50-47.70) mug/L, while females showed 1st test: B 5.20 (0.50-22.60) mug/L; mx Resp 14.00 (3.50-36.70) mug/L 2nd test B 3.60 (0.75-27.00) mug/L; Mx Resp 13.00 (3.70-28.10) mug/L. The statistical comparison (Mann Whitney test) showed significant differences between both sexes in basal values of the first and second test (p<0.001), and in the naximal response of the first test (p<0.03). The statistical analysis did not show significant differences in delta increases between males and females, neither in the first AST nor in the second one. Considering GH values =3 mug/L as a positive response, 4 males exhibited insufficient responses in both tests and other 2 males showed discordant results between tests 1 and 2. All females evaluated produced responses above 3 mug/L in both tests. The results of the present study demonstrate that, particularly in men, AST has no clear limit of normality while it shows good intra-individual reproducibility. In conclusion, at present the biochemical diagnosis of AGHD requires a clear and precise standardization which includes all variables that can modify the GH response to the stimulus used.

Enfermedad de Graves infanto-juvenil: tratamiento alternativo con 131I / Graves disease in childhood and youth: alternative treatment with 131I

Entre 1982 y 1988 se realizó tratamiento y seguimiento de 22 pacientes con enfermedad de Graves infanto-juvenil (13f y 90m). Las edades de comienzo de la enfermedad oscilaron entre 4 y 17 años (x12 a 10m). En todos los casos se efectuó tratamiento con metimazol (MMI) y una vez alcanzado el eutiroidismo, conMMI + hormona tiroidea, con una duración de 1 a 2 meses (m) a 6 años (a). Siete pacientes remitieron con esta terapéutica, 3 abandonaron la consulta, 6 continúan en tratamiento y en 7 se administró una dosis terapéutica (DT) de I (3). En estos últimos (4f y 3m), la edad al recibir la DT oscilaba entre 15 y 20 a.(x17a. 1m.). En 4 casos se indicó el I por remisión luego de administrar MMI por lapsos mayores a 4 años, en 1 caso por recidiva al año de suspender el MMI y en 2 por no ccumplimiento del tratamiento. Las DT variaron entre 4 y 15 mCi (x7,322). Cuatro pacientes remitieron con la 1ra. dosis, 2 requirieron una 2§ DT y en 1 caso fue necesario suministrar una 3ra. Con un seguimiento de 10m. a 2 a. 1 m., 3 pacientes permanecen eutiroideos y 4 presentan hipotiroidismo, que se manifstó entre 2 y 10 m. post DT. No se observaron alteraciones hematológicas, nódulos tiroideos ni aparición o agravamiento de oftalmopatía preexistente. Consideramos que la DT de I(3) constituye un recurso alternativo de alta eficacia en los pacientes infanto-juveniles en quienes ha fracasado la terapéutica antitiroidea, en aquellos en que no se logra la continuidad del tratamiento o ante la aparición de efectos colaterales graves