Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0151744 (myocardial ischemia)
 31,282 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Iodine-131 (I-131) ablation of thyroid remnant and/or persistent, recurrent or metastatic tumour is part of the initial and subsequent management of well-differentiated thyroid carcinoma. Key to optimizing the safety and efficacy of radioablation is maximizing the selective uptake of radioiodine by normal or neoplastic thyroid tissue. This is achieved by ensuring adequate serum concentrations of thyroid-stimulating hormone (TSH). Exogenous TSH administration obviates the thyroid hormone suppression therapy withdrawal that is necessary for endogenous TSH elevation. It also avoids the marked morbidity, discomfort, and impairment in professional and educational pursuits and quality of life that often result from such withdrawal. Multicentre clinical studies have documented the safety and efficacy of recombinant human TSH (rhTSH) in promoting radioiodine uptake in the diagnostic scanning of well-differentiated thyroid cancer. Study of the use of rhTSH to facilitate radioablation of remnant and malignant thyroid tissue is at an earlier stage, with formal clinical investigation underway. Since April 1995, however, rhTSH has been employed as a radioablative adjunct in over 100 patients in the manufacturer's Compassionate Use Program. Twelve of these cases, reported or reviewed in the present paper, provide preliminary evidence that rhTSH is safe and effective in the radioablation setting. More data are needed to confirm these observations and to provide guidelines for optimal radioiodine dosing, and should be furnished by ongoing clinical investigation. rhTSH is the only acceptable treatment option in a subgroup of patients with well-differentiated thyroid cancer, including those with hypopituitarism, ischaemic heart disease, a history of "myxoedema madness," debilitation due to very advanced disease or inability to produce TSH due to continued production of thyroxine by thyroid remnant or metastatic tumour. Therapeutic use of rhTSH may be considered in an increasing number of other cases.
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PMID:Recombinant human thyroid-stimulating hormone (rhTSH) in the radioablation of well-differentiated thyroid cancer: preliminary therapeutic experience. 1072 3

Recombinant TSH is effective in providing exogenous TSH stimulation for patients with differentiated thyroid cancer on thyroid hormone-suppressive therapy. It allows for detection of thyroid remnant and metastases by radioiodine scan and by serum thyroglobulin determination. The sensitivity and image quality of the WBS are similar after rTSH and after THSH withdrawal in the majority of patients. The equivalent 100% sensitivity of rTSH- and withdrawal-stimulated serum thyroglobulin measurement alone in identifying patients with radioiodine uptake outside the thyroid bed [38] may eventually lead to more extensive use of serum thyroglobulin testing after rTSH, with more selective application of radioiodine WBS [39]. Currently, a phase IV trial is in progress to evaluate the efficacy of rTSH-stimulated thyroglobulin levels as the primary modality for long-term follow-up of low risk thyroid cancer patients. The use of rTSH prevents the morbidity, metabolic impairment and the risk of tumor progression associated with THST withdrawal, because of shorter exposure time to elevated TSH [38]. Furthermore, it decreases the radiation exposure of healthy tissues due to faster iodine clearance in euthyroidism. rTSH is well tolerated, with transient nausea in 10.5% and headache in 7.3% of patients. No antibodies specific to rTSH were documented, even after multiple courses of the drug. Currently, rTSH is suggested for patients who do not respond to hormone withdrawal or cannot tolerate hypothyroidism. For patients with low risk of tumor recurrence, rTSH-stimulated testing may be used at 6-12 months after postoperative I-131 ablation and with a repeat cycle of rTSH one year later, followed by testing every 3-5 years. In high risk patients, one set of negative I-131 scan and thyroglobulin test results after hormone withdrawal are recommended before using rTSH testing, because of a greater sensitivity of the withdrawal scan and because rTSH is not currently approved for subsequent I-131 therapy often indicated in these patients [24]. Subsequently, two cycles of rTSH testing are recommended at 6-12 month intervals, followed by testing every 1-3 years for at least the first decade after initial diagnosis. The cost of this commercially available form of rTSH has been considered a major impediment to its common use; however, this should be weighed against the loss of productivity of working hours related to withdrawal [40]. In the therapeutic setting, rTSH is the only acceptable option in a subgroup of patients with hypopituitarism, ischemic heart disease, a history of "myxedema madness," debilitation due to advanced disease, or inability to elicit TSH elevation due to continued production of thyroxine by thyroid remnant or metastatic tumor [33,38]. In conclusion, recombinant TSH facilitates the management of patients with differentiated thyroid carcinoma. It increases the sensitivity of thyroglobulin testing during thyroid hormone suppression therapy and enables radioiodine uptake for whole-body scan and occasionally for radioiodine therapy, without the need for prolonged THST withdrawal and its associated hypothyroidism, reduced quality of life and risk of tumor progression.
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PMID:Recombinant thyroid-stimulating hormone in differentiated thyroid cancer. 1172 83

National Council on Radiation Protection and Measurements Commentary 27 examines recent epidemiologic data primarily from low-dose or low dose-rate studies of low linear-energy-transfer radiation and cancer to assess whether they support the linear no-threshold model as used in radiation protection. The commentary provides a critical review of low-dose or low dose-rate studies, most published within the last 10 y, that are applicable to current occupational, environmental, and medical radiation exposures. The strengths and weaknesses of the epidemiologic methods, dosimetry assessments, and statistical modeling of 29 epidemiologic studies of total solid cancer, leukemia, breast cancer, and thyroid cancer, as well as heritable effects and a few nonmalignant conditions, were evaluated. An appraisal of the degree to which the low-dose or low dose-rate studies supported a linear no-threshold model for radiation protection or on the contrary, demonstrated sufficient evidence that the linear no-threshold model is inappropriate for the purposes of radiation protection was also included. The review found that many, though not all, studies of solid cancer supported the continued use of the linear no-threshold model in radiation protection. Evaluations of the principal studies of leukemia and low-dose or low dose-rate radiation exposure also lent support for the linear no-threshold model as used in protection. Ischemic heart disease, a major type of cardiovascular disease, was examined briefly, but the results of recent studies were considered too weak or inconsistent to allow firm conclusions regarding support of the linear no-threshold model. It is acknowledged that the possible risks from very low doses of low linear-energy-transfer radiation are small and uncertain and that it may never be possible to prove or disprove the validity of the linear no-threshold assumption by epidemiologic means. Nonetheless, the preponderance of recent epidemiologic data on solid cancer is supportive of the continued use of the linear no-threshold model for the purposes of radiation protection. This conclusion is in accord with judgments by other national and international scientific committees, based on somewhat older data. Currently, no alternative dose-response relationship appears more pragmatic or prudent for radiation protection purposes than the linear no-threshold model.
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PMID:Recent Epidemiologic Studies and the Linear No-Threshold Model For Radiation Protection-Considerations Regarding NCRP Commentary 27. 3058 71