MRI & Hypogonadism
Is there a danger to having a MRI to rule out a pituitary tumour when found to have hypogonadotropic hypogonadism? Would you like to have unnecessary brain surgery or put on a drug for no reason? In almost every clinical situation, there is absolutely no need for a MRI. The indication for a MRI is clear. In hypogonadotropic hypogonadism, a MRI is performed only under the clinical context where there are central mass symptoms (visual disturbance, headaches, etc.) and an elevated prolactin.
The frequency of pituitary tumors in the general population and hypogonadotropic hypogonadism is the same. Confirmation and corroboration of this fact is in a study of hypogonadal men with impotence and a variety of endocrine patterns investigating the usefulness of MRI of the brain. The conclusion stated, "Magnetic resonant imaging or computed tomography imaging was available and reviewed in all patients with secondary [hypogonadotropic] hypogonadism. Ten [percent] of these patients had hypothalamic-pituitary imaging abnormalities. The prevalence of pituitary tumors within our population was not significantly elevated compared to the previous general population studies.” Significantly, none of the men with low LH with low TT or FT (hypogonadotropic hypogonadism) had an adenoma or pituitary/hypothalamic mass. [EL Rhoden et al., The value of pituitary magnetic resonance imaging in men with hypogonadism, 170 J Urol 795 (2003).] Therefore, a factor other than hypogonadotropic hypogonadism is necessary to discern a population at risk for hypothalamic-pituitary mass lesions.
Magnetic resonance imaging (MRI) of the hypothalamic-pituitary region did not show any tumors in patients with hypogonadotropic hypogonadism in the study by S. Bajaj et al., Magnetic Resonance Imaging of the Brain in Idiopathic Hypogonadotropic Hypogonadism, Clinical Radiology (1993) 48, 122-124.
The study by Citron, J.T., Ettinger, B., Rubinoff, H., Ettinger, V.M., Minkoff, J., Hom, F., et al. (1996). Prevalence of hypothalamic-pituitary imaging abnormalities in impotent men with secondary hypogonadism. J Urol, 155(2), 529-533 states, “extensive evaluation of all men with secondary hypogonadism is unwarranted because the yield of hypothalamic or pituitary imaging abnormalities identified by this precaution (MRI) is low.”
Multiple, peer-reviewed studies showing there is no diagnostic benefit or need to perform magnetic resonance imaging (MRI) studies to check for a pituitary tumor with an abnormal low testosterone coupled with a low or normal LH, hypogonadotropic hypogonadism, absent any central mass effects with a normal prolactin. Similarly, published medical literature has shown that the use of hypothalamic-pituitary imaging in the evaluation of impotence in elderly men, in the absence of clinical characteristics of other hormonal loss or sella compression symptoms is unnecessary. The standard of care is not to perform an MRI in hypogonadotropic hypogonadism absent central mass symptoms or an elevated prolactin level.
The majority of patients with hypogonadotropic hypogonadism secondary to tumors have multiple pituitary hormone deficiencies in addition to gonadotropin deficiency. In adults, prolactin-secreting pituitary tumors are the most common tumors causing hypogonadotropic hypogonadism. In a study of 656 patients with hypogonadotropic hypogonadism an MRI was performed to screen for hypothalamic pituitary pathology only in patients (Total=18) with an elevated prolactin. The male individuals with hypogonadotropic hypogonadism with a normal prolactin did not undergo magnetic resonance imaging (MRI) studies to check for tumors or other pathology. [AT Guay AT et al., Characterization of Patients in a Medical Endocrine-Based Center for Male Sexual Dysfunction, 5 Endocr Pract 314 (1999).]
For a test to be appropriate, it must discriminate between a normal individual and a diseased individual. A diagnostic test must demonstrate the test is accurate at identifying the disease in affected patients from those in normal individuals. The test should not subject the patient to additional risk of harm; and medical literature should support use of the test if less invasive or expensive tests are not able to provide the physician with the same diagnostic information. This is an absolute for a test to be diagnostic and of any therapeutic value. Otherwise, unnecessary testing or treatments, including surgery, will occur in individuals with pathology of no import to their health.
Diagnostic test is a test used in the clinical environment on individuals with clinical signs or other clinical information consistent with the presence of the condition. The presence of disease has been recognized and the disease of interest is one of the differential diagnoses. This fact raises the expected prevalence (the clinician's estimate of the probability that the individual has the disease based on what the clinician knows to that point) prior to performing the test and thus changes the test performance considerably compared to the situation when the same test is used as a screening test (the probability that a randomly selected individual has the disease is the prevalence of the disease in that population). Affected individuals are more likely to have more prominent disease manifestations in the clinical setting, meaning that the spectrum of disease is generally more severe for in a diagnostic than in a screening setting.
The cascade effect is a process that proceeds in a stepwise fashion from an initiating event to a seemingly inevitable conclusion. With regard to medical technology, the term refers to a chain of events initiated by an unnecessary test, an unexpected result, or patient or physician anxiety, which results in an ill-advised tests or treatments that may cause avoidable adverse effects and/or morbidity. Common triggers of the cascade effect include failing to understand the likelihood of false-positive results, errors in data interpretation, overestimating benefits or underestimating risks, and low tolerance of ambiguity.
Examples of the cascade effect include discovery of endocrine incidentalomas on the head and body. Published medical literature states, "n patients with an incidental asymptomatic pituitary microadenoma, a single PRL test may be the most cost-effective management strategy" that determines further medical care. [JT King et al., Management of incidental pituitary microadenomas: a cost-effectiveness analysis, 82 J Clin Endocrinol Metab 3625 (1997).]
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