RESUMEN
Subacute thyroiditis conventionally recovers without after-effect. Nevertheless some data relate a 5 to 9% occurrence of final hypothyroidism 6 months after the acute stage. We herein studied end-stage hypothyroidism occurrence and effect of thyroid volume alterations on hormonal course during thyroiditis. Twenty-nine cases of subacute thyroiditis were studied. Final thyroid function remained normal in 15 patients (51%) and undetermined in 5 patients (17%). Final hypothyroidism (TSH: 4.5-14.5 microU/mL) occurred in 9 patients (31%). Mean thyroid volume was increased in acute stage in patients with final normal thyroid function (16.6+/-5.7cm(3)) and decreased by 63% during follow-up; final mean thyroid volume was 6.1+/-1.3cm(3). Mean thyroid volume was normal in acute stage in final hypothyroid patients (10.7+/-3.0cm(3)) and decreased by 72% during follow-up; final mean thyroid volume was 3.3+/-1.1cm(3). End-stage mean thyroid volume was significantly lower in final hypothyroid patients (p<0.05) compared to patients with final normal thyroid function. We conclude that the occurrence of final hypothyroidism is underestimated after subacute thyroiditis. Ultrasonographic follow-up might be helpful in the detection of final hypothyroid-risk patients: thyroid volume not increased in acute stage and lower than 5cm(3) during follow-up is one of the ultrasonographic features of these patients.
Asunto(s)
Hipotiroidismo/diagnóstico por imagen , Hipotiroidismo/etiología , Tiroiditis Subaguda/complicaciones , Enfermedad Aguda , Adulto , Sesgo , Femenino , Estudios de Seguimiento , Humanos , Hipotiroidismo/sangre , Hipotiroidismo/epidemiología , Hipotiroidismo/patología , Incidencia , Masculino , Persona de Mediana Edad , Valor Predictivo de las Pruebas , Factores de Riesgo , Pruebas de Función de la Tiroides , Tirotropina/sangre , Ultrasonografía/métodos , Ultrasonografía/normasRESUMEN
Changes in photochemical efficiency, non-radiative energy dissipation (NRD), de-epoxidation state of xanthophyll cycle components (DPS) and contents of the antioxidants ascorbic acid and glutathione were studied in leaves of the poikilohydric Ramonda serbica Panc. (Gesneriaceae) during cycles of dehydration and subsequent rehydration. In drying leaves, the intrinsic efficiency of PS II photochemistry and the photon yield of PS II electron transport showed strong progressive decreases. Simultaneously, the fraction of excitation energy dissipated as heat in the PS II antenna increased markedly. The energy-dependent component of non-photochemical quenching (NPQ) showed an increase in dehydrating leaves down to relative water contents (RWC) values near 30%. Further decreases in RWC below these values caused a decrease in NPQ. Accordingly, DPS showed a similar behaviour, with a sharp increase and a subsequent decrease at very low RWC, although the maximum DPS was reached at slightly lower RWC than that for the maximum NPQ. The pools of reduced ascorbate and glutathione increased strongly when the RWC values fell below 40% and remained high in fully dehydrated leaves. When plants were re-watered photosynthetic efficiency, NRD, DPS and antioxidant contents recovered their initial control values. However, during rehydration, the zeaxanthin content showed a transient increase, as did NPQ, indicating an increasing demand for non-radiative dissipation. On the other hand, the contents of reduced ascorbate and reduced glutathione decreased but were still relatively high in the initial phase of rehydration, when the rate of photosynthetic electron transport, proton pumping and NRD were still relatively low. These results indicate that several photoprotective mechanisms are operating in R. serbica. Protection from photo-oxidation and photoinhibition appears to be achieved by co-ordinated contributions by ascorbate, glutathione and zeaxanthin-mediated NPQ. This variety of photoprotective mechanisms may be essential for conferring desiccation-tolerance.