Objective: The aim of the present study was to compare the effects of iopanoic acid (IOP) or a saturated solution of potassium iodide (SSKI) administration to patients with toxic diffuse goiters (TDG). Design: Patients with TDG are treated with thionamides and high doses of iodine preoperatively. In this study, two types of preoperative drug regimens were used: propylthiouracil or methimazole plus SSKI for 10 -15 days ðn ¼ 8Þ or IOP for 7 days ðn ¼ 6Þ: Methods: Serum thyroid hormones (total and free thyroxine (T 4 ), total tri-iodothyronine (T 3 ) and reverse T 3 (rT 3 ), were evaluated after 7 days of either SSKI or IOP treatment, and after 10 -15 days of SSKI administration. During thyroidectomy, samples of thyroid gland were obtained to evaluate thyroperoxidase and thyroid H 2 O 2 -generating activities. Results: Serum total T 3 was significantly decreased after 7 days of either treatment, and serum rT 3 was significantly increased in IOP-treated patients. Serum total and free T 4 were unaffected by 7 days of IOP treatment, but decreased after 7 days of SSKI treatment, although significantly diminished levels were only reached after a further 3-8 days of SSKI administration. During both drug regimens, serum TSH remained low (SSKI: 0:159^0:122; IOP: 0:400^0:109 mU=ml). Thyroperoxidase activity was significantly lower in thyroid samples from patients treated with SSKI for 10-15 days than in the thyroid glands from IOP-treated patients. However, thyroid H 2 O 2 generation was inhibited in samples from patients treated with either IOP or SSKI. Conclusions: We show herein that IOP treatment can be effective in the management of hyperthyroidism and that this drug inhibits thyroid NADPH oxidase activity, just as previously described for SSKI, probably due to its iodine content.

A calcium and NAD(P)H-dependent H(2)O(2)-generating activity has been studied in paranodular thyroid tissues from four patients with cold thyroid nodules and from nine diffuse toxic goiters. H(2)O(2) generation was detected both in the particulate (P 3,000 g) and in the microsomal (P 100,000 g) fractions of paranodular tissue surrounding cold thyroid nodules (PN), with the same biochemical properties described for NADPH oxidase found in porcine and human thyroids. In PN tissues, the particulate NADPH oxidase activity (224 +/- 38 nmol H(2)O(2) x h(-1) x mg(-1) protein) was similar to that described for the porcine thyroid enzyme. However, no NADPH oxidase activity was detectable in the particulate fractions from eight diffuse toxic goiter patients treated with iodine before surgery; all but one also received propylthiouracil or methimazole in the preoperative period. Thyroid cytochrome c reductase (diffuse toxic goiters = 438 +/- 104 nmol NADP(+) x h(-1) x mg(-1) protein; PN = 78 +/- 10 nmol NADP(+) x h(-1) x mg(-1) protein) and thyroperoxidase (diffuse toxic goiters = 621 +/- 179 U x g(-1) protein; PN = 232 +/- 121 U x g(-1) protein) activities were unaffected by iodide. Thus, the human NADPH oxidase seems to be inhibited by iodinated compounds in vivo and probably is an enzyme involved in the Wolff-Chaikoff effect. Our findings reinforce the hypothesis that thyroid NADPH oxidase is responsible for the production of H(2)O(2) necessary for thyroid hormone biosynthesis.

A acromegalia é uma síndrome causada pela hipersecreção do hormônio de crescimento (GH). No entanto, alguns pacientes podem apresentar níveis séricos limítrofes, ou mesmo dentro da normalidade, dificultando o diagnóstico. Relatamos um caso de acromegalia cuja investigação diagnóstica inicial evidenciou níveis séricos basais de GH dentro dos limites da normalidade e tomografia computadorizada (TC) de sela túrcica normal. A confirmação da doença só foi estabelecida através de testes dinâmicos que avaliam a regulação do GH (dosagem de GH durante o teste oral de tolerância à glicose e após TRH) e confirmada pela ressonância nuclear magnética (RNM) de sela túrcica que evidenciou imagem sugestiva de microadenoma. A paciente foi submetida à cirurgia hipofisária pela via de acesso oronaso esfenoidal e a área tumoral encaminhada para estudo imunohistoquímico, corroborando o diagnóstico de acromegalia. A avaliação dinâmica no pós operatório evidenciou regulação normal do GH. Discutimos os critérios diagnósticos da acromegalia, com ênfase na importância de se prosseguir com a investigação sempre que houver uma forte suspeita clínica, mesmo que os exames iniciais se apresentem dentro dos limites da normalidade. ABSTRACTAcromegaly is a syndrome caused by growth hormone (GH) hypersecretion. However, some patients can present normal or near normal levels of GH, difficulting diagnosis. We report an acromegalic patient with normal levels of GH and negative imaging at initial investigation. Acromegaly was confirmed by dynamic tests (glucose tolerance test and GH-TRH), and RMI was suggestive of a microadenoma. The patient was submitted to a transesphenoidal pituitary surgery and imunohistochemistry study, corroborating the diagnosis of acromegaly. Dynamic tests performed after surgery evidenced normal GH regulation. Considerations on the diagnosis of acromegaly were also done, emphasizing the importance of continuing the investigation whenever clinical suspicion persists, even though the initial tests are within the normal range.