Scielo RSS <![CDATA[Revista médica de Chile]]> http://www.scielo.cl/rss.php?pid=0034-988720050009&lang=es vol. 133 num. 9 lang. es <![CDATA[SciELO Logo]]> http://www.scielo.cl/img/en/fbpelogp.gif http://www.scielo.cl <![CDATA[<B>¿Crónica de una pandemia anunciada?</B>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0034-98872005000900001&lng=es&nrm=iso&tlng=es In the last years our country has been affected by several outbreaks of infectious diseases such as Cholera and Hanta virus and recently, by pathogens associated to red tide. Chile was able to manage those emergencies using the local health system. The new threat that may emerge and could eventually overcome that capacity, is the possible H5N1 influenza virus outbreak. Influenza is responsible for the most destructive pandemic, the Spanish influenza, that killed over 40 million individuals in 1918. The new influenza strain (H5N1) is at present endemic in poultry in Asia and has been associated to human fatal cases in Hong Kong and Vietnam. Even though this strain is not able yet to be transmitted among humans, evidence has accumulated that such ability could be reached by the new strain, since it was already detected in pigs. That particular evidence may indicate that the virus could adapt to infect humans, since a similar situation was observed in several of the influenza pandemics. The World Health Organization set a "task force" to develop a strategy that may help to control the virus spread. Several countries are already stocking anti-flu drugs and others are developing new vaccine that are currently been assayed in human volunteers. It is possible that we may have a vaccine before the outbreak; this development is even faster than for SARS. The mayor question to be addressed for developing countries is: What will be done if we do not have the vaccine on time? (Rev Méd Chile 2005; 133: 999-1001). <![CDATA[<B>Predictores de eventos cardiovasculares no fatales en una comunidad urbana en Chile</B>: <B>experiencia de seguimiento Proyecto San Francisco</B><A HREF="#1"><B><SUP>*</B></SUP></A>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0034-98872005000900002&lng=es&nrm=iso&tlng=es Background: The San Francisco Project is a prospective study aiming to determine the most important cardiovascular risk factors in the Chilean population. Aim: To report the results of the San Francisco Project after a mean follow up of five years. Material and methods: Between 1997 and 1999, 920 subjects (aged 39.5 ± 16.3 years, 382 males), free of cardiovascular events, were examined to determine their cardiovascular risk factors. The prevalence of risk factors was compared with the Chilean National Health Survey. All non fatal cardiovascular events were registered until 2003. A logistic regression model including gender, obesity, family history, educational level and classical cardiovascular risk factors, was performed to identify independent predictors of cardiovascular events. Results: The prevalence of cardiovascular risk factors in the studied population was similar to that of the Chilean National Health Survey, except for serum lipid levels, that were lower in the latter. The mean follow up was 5.3 ± 0.3 years (range 4-6 years), and 26 cardiovascular events were registered. The independent predictors of these events were age, with a relative risk (RR) of 4.3 and 95% confidence intervals (CI) of 1.9 to 9.5 (p <0.001), high blood pressure with a RR of 5.2 (95% CI 2.3-11.7, p <0.001), diabetes mellitus with a RR of 4.5 (95% CI 1.9-10.7, p <0.01) and a low socioeconomic level with a RR of 3.5 (95% CI 1.5-7.9, p <0.01). The model did not accept serum lipid levels, smoking and alcohol intake as independent predictors. Conclusions: In this cohort of Chilean people, the independent predictors of non fatal cardiovascular events were high blood pressure, diabetes mellitus and a low socioeconomic level (Rev Méd Chile 2005; 133: 1002-12). <![CDATA[<B>Evolución del estado del estado nutricional de escolares chilenos de 6 años (1987- 2003)</B>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0034-98872005000900003&lng=es&nrm=iso&tlng=es Background: As a consequence of the epidemiological transition in Chile, the nutritional status of the population has changed notoriously. Aim: To study the changes in the nutritional status of six years-old Chilean children from 1987 to 2003. Material and Methods: The computer data base of a government institution in charge of the School Lunch Program (JUNAEB) was used. It contains data on weight, height, sex and date of birth of six years old children, in the years 1987, 1990, 1993, 1996, 2000, 2001, 2002 and 2003. Results: The data of approximately 80,000 children was analyzed. Both weight and height increased over the study years. There was a significant reduction in the number of children with weight deficit but also an increase in the proportion of children with obesity. Stunting was also reduced. The proportion of children with HAZ over 2 SD increased from 0.76 in 1987 to 2.2% in 2003. The prevalence of obesity has not increased since the year 2000. Conclusion: The stabilization in the prevalence of obesity is a positive finding, considering its adverse consequences for health (Rev Méd Chile 2005; 133: 1013-20). <![CDATA[<B>Síntomas depresivos posinfarto al miocardio</B>: <B>detección precoz en una población hospitalizada</B>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0034-98872005000900004&lng=es&nrm=iso&tlng=es Background: Depression after myocardial infarction (MI) is a frequent disorder and it increases the long-term risk of cardiac mortality. Aim: To assess the frequency of depressive symptoms and the history of depression in hospitalized post-MI patients. Patients and Methods: During three months, depressive symptoms and history of depression were studied in 47 consecutive patients (mean age 59,8±9,5 years, 68% male), admitted for MI to the Barros Luco Trudeau Hospital. The Beck Depression Inventory (BDI) and the Composite International Diagnostic Interview (CIDI 2.1) were used with DSM-IV diagnosis criteria. Results: According to the results obtained using the CIDI, 27,7% of the patients had a history of depression. This occurred in 53,3% of women and 15,6% of men (p <0.01). During the hospitalization, 38,3% of patients had depressive symptoms (BDI <FONT FACE=Symbol>&sup3;</FONT> 17 points), affecting 60% of women and 28,1% of men (p <0.02). In women and patients with history of depression, depressive symptoms tended to be more common and more severe. Conclusions: Depressive symptoms in post-MI patients are frequent and attending physicians should actively detect them (Rev Méd Chile 2005; 133: 1021-27). <![CDATA[<B>Tiroidectomía profiláctica en niños y jóvenes con cáncer medular tiroideo hereditario</B>: <B>Experiencia chilena</B>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0034-98872005000900005&lng=es&nrm=iso&tlng=es Background: With the availability of the RET proto-oncogene genetic testing, it is possible to perform prophylactic total thyroidectomy among carriers of RET mutation. Aim: To evaluate the histological findings and the effects of the prophylactic total thyroidectomy in first-degree relatives of Chilean patients with multiple endocrine neoplasia type 2 (MEN 2) based on the Ret proto-oncogen analysis. Subjects and Methods: Nineteen patients belonging to 11 MEN 2 families underwent total thyroidectomy. Of these, 16 either with C cell hyperplasia (CCH) or microscopic medullary thyroid carcinoma (MTC) were selected for the final analysis. Results: The age at the moment of thyroidectomy ranged from 3 to 24 years (median 9.5). The most common mutation was located in codon 634 (69%) followed by codon 620 (25%). Histopathology revealed MTC in 13 patients (81%, youngest 3 years, oldest ones 19 and 24 years) and CCH in 3. A significant correlation was observed between basal preoperative serum calcitonin/tumor size (r= 0.53, P <0.05) and age/tumor size (r= 0.56, P <0.03), but not between basal preoperative serum calcitonin and age. Stimulated preoperative calcitonin levels were confounding and not useful for differentiating CCH from MTC. None of patients in whom cervical dissection was done (9/16) presented lymph node metastases, including the oldest ones. All patients but the older ones were biochemically cured after a mean of 5 years of follow-up. Conclusion: Prophylactic total thyroidectomy should be done early in life because there is an age-dependent progression from HCC to MTC. MTC often precedes biochemical detection of the disease (Rev Méd Chile 2005; 133: 1029-36) <![CDATA[<B>Indicaciones resultados alejados del tratamiento quirúrgico electivo de la enfermedad diverticular del colon sigmoides</B>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0034-98872005000900006&lng=es&nrm=iso&tlng=es Background: There are no clear guidelines for the indication of elective surgery in sigmoid diverticular disease. Aim: To analyze the indications and long term results of elective surgery in sigmoid diverticular disease. Material and Methods: Retrospective review of 100 patients (age range 25-86 years, 51 male) with sigmoid diverticular disease, operated in a lapse of 22 years. Sixty seven patients answered a survey about their disease at the end of follow up. Results: Among patients aged more than 70 years, there was a higher proportion of women. The main indication for surgery was recurrent diverticulitis in 54 patients, followed by diverticular fistula in 19. A sigmoidectomy was performed in 91 patients. Stapled anastomosis was performed in half of these patients. No patient died or required reoperation in the immediate postoperative period. During a follow up ranging from 8 to 280 months, 28 patients died for causes not associated with diverticular disease and five were lost. Those patients that answered the survey were free of symptoms related to diverticular disease and did not require new operations. Conclusions: In patients with sigmoid diverticular disease and recurrent diverticulitis or with fistulae, the long term results of surgery are satisfactory (Rev Méd Chile 2005; 133: 1037-42) <![CDATA[<B>Poliposis familiar</B>: <B>Alternativas terapéuticas y estudio de los familiares</B>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0034-98872005000900007&lng=es&nrm=iso&tlng=es Background: To reduce the mortality associated to Familial Adenomatous Polyposis (FAP), screening of close relatives of patients with the disease is crucial. Aim: To analyze the results of the surgical treatment of patients with FAP, and to evaluate the family screening. Patients and Methods: Clinical records of patients operated in our institution since 1977, were reviewed analyzing surgical and pathological results, and follow up. In their family members, we evaluated and analyzed the performance of screening tests, former surgeries, history of disease-related cancer and mortality, all due to FAP. Results: Between January 1977 and August 2002, 15 patients were operated on. Of these, only 33% consulted on the setting of a familial screening. A proctocolectomy and terminal ileostomy was performed in 27% of patients; 20% had a proctocolectomy and ileal pouch, and 53% underwent a total colectomy with ileo-rectal anastomosis. Morbidity and mortality were 7% and 0%, respectively. Twenty percent had a colorectal cancer. During a median of 68 months follow-up, the disease-related survival was 92%; no cancer of the rectal stump was detected. Of the 122 family members identified, only 33% with clear indication of screening underwent a colonoscopy. Twenty-nine percent had a confirmed FAP and were operated: in 61% of them a colorectal cancer was found, and 91% of these died. Conclusions: The results of the surgical treatment of FAP are satisfactory. Nevertheless, family screening should be improved to reduce the high rates of mortality revealed in the study of other family members (Rev Méd Chile 2005; 133: 1043-50). <![CDATA[<B>Estudio de asociación por desequilibrio de ligamiento entre los genes TGFA, RARA, y BCL3 y fisura labiopalatina no sindrómica (FLPNS) en la población chilena</B>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0034-98872005000900008&lng=es&nrm=iso&tlng=es Background: Nonsyndromic cleft lip/palate (NSCLP) is a congenital malformation with the characteristics of a complex genetic trait. Based on experimental evidences as well as on association and linkage studies candidate genes TGFA, RARA and BCL3 have been postulated as being involved in the genetic etiology of this pathology. Aim: To test the possible association due to linkage disequilibrium between microsatellite markers located at less than 1cM from the three candidate genes and nonsyndromic cleft lip/palate using the case-parents trio design. Patients and Methods: The sample consisted of 58 case-parents trios. Two microsatellite markers, flanking each one of the candidate genes were analyzed by means of the polymerase chain reaction (PCR) with fluorescent labeled microsatellite markers. Electrophoresis of the PCR products was performed on a laser-fluorescent automatic DNA sequencer. Nonparametric ETDT was used to analyze the genotype data. Results: Significant linkage disequilibrium was detected between D2S443 (TGFA) and NSCLP. Significance was almost reached between D17S800 (RARA) and NSCLP. Alleles 239bp (D2S443) and 172bp (D17S800) showed significant preferential transmission from heterozygous parents to affected offspring. In the case of BCL3 both markers showed no significant results. Conclusions: The results of the present study do not show clear evidence that TGFA or RARA could be involved in the genetic etiology of NSCLP. Even though the importance of retinoic acid in the development of the embryo is well documented the results obtained for RARA are difficult to analyze. In relation to the possible role of BCL3 in NSCLP, recent information postulates that other genes located in the same chromosome region could be involved in NSCLP (Rev Méd Chile 2005; 133: 1051-58). <![CDATA[<B>Detección de metapneumovirus humano en niños hospitalizados por infección respiratoria aguda baja en Santiago, Chile</B>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0034-98872005000900009&lng=es&nrm=iso&tlng=es Background: Human metapneumovirus (hMPV) has recently been described as a new causal agent of acute low respiratory infection (ALRI) in children. In South America, detection has been reported only in Brazil and Argentina. Aim: To detect hMPV in children hospitalized for ALRI in Santiago, Chile. Material and Methods: Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect N gene of hMPV in 182 nasopharyngeal aspirates that were negative for common respiratory viruses, obtained from children hospitalized for ALRI during 2003. Results: Ten samples (5.4%) were positive, most of them detected during spring months. Conclusions: Since hMPV was detected among infants with ALRI in Santiago, further studies on their prevalence should be done in South America (Rev Méd Chile 2005; 133: 1059-64) <![CDATA[<B>Oxigenación con membrana extracorpórea en pacientes pediátricos</B>: <B>Comunicación de los 3 primeros casos tratados</B>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0034-98872005000900010&lng=es&nrm=iso&tlng=es Extracorporeal membrane oxygenation (ECMO) improves survival in neonatal and pediatric patients with reversible severe respiratory or cardiac failure, in whom intensive treatment fails. Since 1999, a multidisciplinary team is trained to form the first neonatal-pediatric ECMO center in Chile, according to the norms of the Extracorporeal Life Support Organization (ELSO). During 2003 the first three patients were admitted to the program: a male newborn with pulmonary hypertension, a 38 days old female operated for a total anomalous pulmonary venous connection and a 3 months old male with a severe pneumonia caused by respiratory syncytial virus. They remained in ECMO for five, seven and nine days respectively and all survived to the procedure. No neurological complications were observed after one and a half year of follow up. This consolidates the first national neonatal-pediatric ECMO program, associated to ELSO. Up to date, twelve patients have been admitted to the program (Rev Méd Chile 2005; 133: 1065-70) <![CDATA[<B>Impétigo herpetiforme recurrente</B>: <B>manejo exitoso con ciclosporina</B>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0034-98872005000900011&lng=es&nrm=iso&tlng=es Impetigo Herpetiformis is a high-risk gestational skin disease that represents a risk for both the mother and offspring. Its management is based on multisystemic support and maternal steroid therapy. When these measures are insufficient to control the disease, the association of ciclosporine to the treatment has been proposed. We report a 24 year-old woman with a 16 weeks pregnancy, that presented with Impetigo Herpetiformis. The disease was refractory to the use of steroids, the patient had a metabolic decompensation and a dehydration with electrolyte imbalance. Therefore, treatment with ciclosporine was initiated and a rapid regression of the lesions was observed. Gestation was maintained, with a good perinatal outcome (Rev Méd Chile 2005; 133: 1071-74). <![CDATA[<B>El riesgo de malformaciones congénitas y defectos de la programación genómica, en relación con las técnicas de reproducción asistida y la clonación</B>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0034-98872005000900012&lng=es&nrm=iso&tlng=es Recent studies show that assisted reproductive technologies (ART), whether in vitro fertilization (IVF) or intra-cytoplasmatic sperm injection (ICSI) or applied to cloning by somatic cell nuclear transfer (SCNT) are associated to a higher risk of congenital malformations and errors in deprogramming, maintenance or reprogramming genomic imprinting in humans and animals. IVF and ICSI are also associated to an increased admission to neonatal intensive care units and more need for health care resources in infancy. A mutagenic effect of a chemical used in SCNT has been reported and gene depression was found in bovine embryos obtained by IVF or SCNT. The causes of these anomalies could be pathological conditions for which ART is applied, a direct effect of technologies on the zygotes or embryos, avoidance for zygotes or embryos of the oviduct path that is needed to elicit necessary immunity or genomic programming processes, or adaptive selective steps acquired during thousands of millions of generations in evolution. The knowledge of evolution is emphasized as essential in the scientific ethical analysis (Rev Méd Chile 2005; 133: 1075-80). <![CDATA[<B>Infecciones por <I>Vibrio parahaemolyticus</I> e intoxicaciones por algas</B>: <B>problemas emergentes de salud pública en Chile</B>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0034-98872005000900013&lng=es&nrm=iso&tlng=es There is interest in the paradigm that relates environmental sea changes to the emergence of diseases that affect both aquatic organisms in the sea and human beings. The emergence of Vibrio parahaemolyticus as an important cause of epidemic summer diarrhea in 2004 and 2005, confined mainly to the tenth region in Chile, could be a manifestation of this trend. This and other areas of the country have also experienced several outbreaks of paralytic shellfish poisoning (PSP), diarrheal shellfish poisoning (DSP) and amnesic shellfish poisoning (ASP) caused by harmful algal blooms (HAB) of Alexandrium catenella, Dinophysis acuta and Pseudonitzchia species, respectively. The short historical record of these pathological phenomena in Chile suggests that they are increasing in frequency and expanding their geographical range. The V parahaemolyticus isolates responsible for the Chilean outbreaks correspond mainly to the pandemic strain O3:K6. HAB found in Chile and the intoxications caused by them have similar biological characteristics to those described in other areas of the world. The tenth region, the area where these problems are emerging, produces approximately 80-90% of the shellfish consumed in Chile and a large proportion of the shellfish that is exported. Prevention of these public health problems can be attained by developing policies that increase environmental surveillance for Vibrios and toxic algae, improve the epidemiological surveillance of acute diarrhea and algal intoxications after the ingestion of raw bivalves, and educate the population on the mode of transmission of these diseases. Scientific capacity and laboratories need to be developed to widen the limited knowledge of the biology of Vibrio and toxic algae and the environmental factors that favor their emergence as public health and economic problems in Chile (Rev Méd Chile 2005; 133: 1081-88) <![CDATA[<B>Papel de los polimorfismos -238 y -308 del promotor del factor de necrosis tumoral alfa en la patogenia y respuesta al tratamiento anti- factor de necrosis tumoral alfa en artritis reumatoide</B>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0034-98872005000900014&lng=es&nrm=iso&tlng=es Rheumatoid arthritis (RA) is a systemic autoimmune disease that affects 0.8% of the world population, it affects the synovial membrane of joints and the clinical presentation encompasses a wide spectrum, ranging from a mild to a severe and erosive disease that causes joint and cartilage destruction which finally provokes irreversible structural damage and patient disability. In the last years, there have been important advances in the pathogenesis of this disease, the efforts have been concentrated on pro-inflammatory cytokines such as tumor necrosis factor alpha (TNFalpha). This protein guides numerous events in the synovial and systemic inflammatory process and is encoded in the Major Histocompability Complex (MHC), one of the most polymorphic of the genome. Polymorphisms affecting the TNFalpha gene and its regulatory regions are associated with RA prevalence and course. There is a possible association between these polymorphisms and the clinical response to the use of monoclonal antibodies anti-TNFalpha. The possibility that the determination of genotypes -238 and -308 may have prognostic and therapeutic consequences is debated nowadays (Rev Méd Chile 2005; 133: 1089-95). <![CDATA[<B>Geometría de los sistemas vivos y su importancia en Medicina</B>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0034-98872005000900015&lng=es&nrm=iso&tlng=es We analyze the most relevant concepts about complexity of sciences, showing examples and consequences in medical sciences. In the first section we introduce some basic concepts about fractals and its relationship with the geometry of nature and chaos dynamics. We also introduce notions of critic systems, the role of energy in them and we propose a conceptual model for living systems. In this model we identify the non-linear dynamics as the dynamics of the living forms and fractals as the form resulting from that dynamics. In the second section we review medical and biological examples: infectious diseases, cardiovascular and behavior dynamics, from which useful concepts and medical hypotheses emerge. One of the most important concepts, is the proposition that homeostasis would have an irregular dynamic. Then, we could expect that healthy individuals should be characterized by irregular dynamics, but old or sick individuals would change, probably decreasing the complexity of its dynamics. Therefore, we ask ourselves if the use of therapies to obtain a constant internal medium can be a mistake (Rev Méd Chile 2005; 133: 1097-107) <![CDATA[<B>Medicina genómica ¿Privilegio de los países desarrollados?</B>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0034-98872005000900016&lng=es&nrm=iso&tlng=es Genomic medicine is defined as the application of the knowledge originating from the Human Genome Project in health sciences. It has a vertiginous advance in developed countries, but its use in developing regions is scanty. This contributes to global health inequalities, stressing one of the greatest ethical problems that mankind is facing. In a study leaded by the University of Toronto Center of Bioethics, 28 highly qualified scientists elaborated a list of the ten most important biotechnologies to improve public health in developing countries. Several of these technologies are successfully applied in countries such as China, Cuba and Mexico. The factors that are hindering the application of such technologies in Chile, are briefly discussed (Rev Méd Chile 2005; 133: 1108-10) <![CDATA[<B>Intervalos de Confianza</B>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0034-98872005000900017&lng=es&nrm=iso&tlng=es Genomic medicine is defined as the application of the knowledge originating from the Human Genome Project in health sciences. It has a vertiginous advance in developed countries, but its use in developing regions is scanty. This contributes to global health inequalities, stressing one of the greatest ethical problems that mankind is facing. In a study leaded by the University of Toronto Center of Bioethics, 28 highly qualified scientists elaborated a list of the ten most important biotechnologies to improve public health in developing countries. Several of these technologies are successfully applied in countries such as China, Cuba and Mexico. The factors that are hindering the application of such technologies in Chile, are briefly discussed (Rev Méd Chile 2005; 133: 1108-10) <![CDATA[<B>Análisis crítico de un artículo:La terapia de reemplazo con la combinación de T3 con T4 no sería mejor que T4 sola en pacientes hipotiroideos</B>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0034-98872005000900018&lng=es&nrm=iso&tlng=es Conflicting results have recently been published about the benefits of combined thyroxine (T4) and triiodothyronine (T3) in treating hypothyroid patients. However these studies may have been underpowered to detect differences in psychological well-being specifically related to thyroxine replacement. We conducted a large, double-blind, randomized controlled trial of partial substitution of 50 microg of T4 by 10 microg of T3 (T3) vs placebo (T4 alone - 50 microg of T4 replaced) in 697 hypothyroid patients. Thyroid function showed a rise in the TSH (132%), a fall in Free T4 (35%, P <0.001) and unchanged basal Free T3 levels (P=0.92). At 3 months there was a large (39%) «placebo effect» improvement in «psychiatric caseness» defined by the General Health Questionnaire 12 score (GHQ 12) in the control group compared with baseline and this was sustained at 12 months. Differences vs the intervention (T3) group were more modest with improvements in GHQ caseness (OR - 0.61; 95% CI: 0.42, 0.90; P=0.01) and HADS anxiety scores at 3 months (P <0.03) but not GHQ Likert scores, HADS depression, thyroid symptoms or visual analog scales of mood and the initial differences were lost at 12 months. These results may be consistent with a subgroup of patients showing transient improvement following partial substitution with T3 but do not provide conclusive evidence of specific benefit from partial substitution of T4 by T3 in patients on thyroxine replacement. They also emphasize the large and sustained «placebo effect» that can follow changes in thyroid hormone administration <![CDATA[<B>universal de bioética y derechos humanos de UNESCO</B>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0034-98872005000900019&lng=es&nrm=iso&tlng=es Conflicting results have recently been published about the benefits of combined thyroxine (T4) and triiodothyronine (T3) in treating hypothyroid patients. However these studies may have been underpowered to detect differences in psychological well-being specifically related to thyroxine replacement. We conducted a large, double-blind, randomized controlled trial of partial substitution of 50 microg of T4 by 10 microg of T3 (T3) vs placebo (T4 alone - 50 microg of T4 replaced) in 697 hypothyroid patients. Thyroid function showed a rise in the TSH (132%), a fall in Free T4 (35%, P <0.001) and unchanged basal Free T3 levels (P=0.92). At 3 months there was a large (39%) «placebo effect» improvement in «psychiatric caseness» defined by the General Health Questionnaire 12 score (GHQ 12) in the control group compared with baseline and this was sustained at 12 months. Differences vs the intervention (T3) group were more modest with improvements in GHQ caseness (OR - 0.61; 95% CI: 0.42, 0.90; P=0.01) and HADS anxiety scores at 3 months (P <0.03) but not GHQ Likert scores, HADS depression, thyroid symptoms or visual analog scales of mood and the initial differences were lost at 12 months. These results may be consistent with a subgroup of patients showing transient improvement following partial substitution with T3 but do not provide conclusive evidence of specific benefit from partial substitution of T4 by T3 in patients on thyroxine replacement. They also emphasize the large and sustained «placebo effect» that can follow changes in thyroid hormone administration