ISSN:1051-2144    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

&NA;Nelson's syndrome is the clinical progression of an ACTH‐secreting pituitary adenoma that occurs in patients adrenalectomized for Cushing's disease. These pituitary tumors differ from those before adrenalectomy by their sometimes aggressive growth potential. Additionally, their ACTH secretion is much less suppressible by administration of glucocorticoids than in the stage of Cushing's disease. Nelson's tumor cells differ to some degree from those from Cushing's tumors. Recent research underscores the intriguing possibility that somatic mutations in the glucocorticoid receptor gene might contribute to its pathogenesis. The incidence of Nelson's syndrome after adrenalectomy is still a matter of dispute, in part explained by lack in uniformity of definition of the syndrome. Because Nelson's tumors are often locally invasive, neurosurgery, either trans‐ or suprasphenoidally, is the treatment of first choice. Postoperative radiotherapy is indicated in patients with residual tumor or extracellular extension. Recent reports claim benefit from long‐acting somatostatin analogues, although long‐term success remains to be assessed. Notwithstanding improved treatment, Nelson's syndrome shares with Cushing's disease the inevitable tendency to recur. Therefore, life‐long management of these patients is mandatory.

ISSN:1051-2144    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

&NA;Loss of bone during extended space flight has long been a concern that could limit the ability of humans to explore the universe. Surprisingly, the available data do not support the concept that weightlessness leads inexorably to a depleted skeleton unable to withstand the stress of a return to a 1‐g environment. Nevertheless, some bone loss does occur, especially in those bones most stressed by gravity prior to flight, which provides confirmation of the proposal formulated over a century ago by Julius Wolff that mechanical stress determines the form and function of bone. Although the phenomenon of bone loss with skeletal unloading, whether by space flight or immobilization or just taking a load off your feet (literally) is well established, the mechanisms by which bone senses load and adjusts to it are not so clear. What actually is the stimulus, and what are the sensors? What are the target cells? How do the sensors communicate the message into the cells, and by what pathways do the cells respond? What is the role of endocrine factors vs. paracrine or autocrine factors in mediating or modulating the response? None of these questions has been answered with certainty, but, as will become apparent in this review, we have some some clues directing us to the answers. Although the focus of this review concerns space flight, it seems highly likely that the mechanisms mediating the transmission of mechanical load to changes in bone formation and resorption apply equally well to all forms of disuse osteoporosis and are likely to be the same mechanisms affected by other etiologies of osteoporosis.

ISSN:1051-2144    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

&NA;The growth hormone (GH)/insulin‐like growth factor (IGF) axis is an essential component of the endocrine system for stimulating postnatal growth in children and maintaining lean body mass in adults. It may be more than coincidental, therefore, that impaired growth and muscle wasting are common symptoms of human immunodeficiency virus (HIV) infection in children and adults. Wasting and growth failure contribute significantly to the morbidity and mortality associated with AIDS. Multiple defects in the GH/IGF axis have been reported in patiients with AIDS. These include abnormal GH secretion and tissue responsiveness, diminished serum concentrations of IGF‐I and ‐II, and abnormall post‐translational modifications of IGF binding proteins. In this review we examine the hypothesis that the failure to thrive (in children) and the loss of lean body mass (in adults) may be age‐related manifestations of AIDS that, in part, result from defects in the GH/IGF axis.

ISSN:1051-2144    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

&NA;HIV infection is associated with a number of endocrine and metabolic manifestations involving the adrenal, gonadal, thyroid, and growth hormone (GH)‐insulin‐like growth factor‐I axes. Endocrine dysfunction may result rarely from end‐organ and/or pituitary/hypothalamic tissue destruction from opportunistic infections, direct effects of the HIV virus, and/or indirect effects of associated cytokines on hormonal metabolism. New medications used in the treatment of HIV disease, such as Megace®, may also have profound effects on endocrine function. Adrenal insufficiency and/or impaired adrenal reserve are increasingly recognized in this population, suggesting the need for screening in the appropriate clinical context. In addition, hormonal adaptation to stress, severe illness, and protein calorie malnutrition in patients with AIDS may also effect endocrine function, resulting in decreased androgen levels and acquired GH resistance. Moreover, the loss of potent endogenous anabolic hormones such as testosterone and GH may in turn contribute independently to the severe and disproportionate loss of lean body mass characteristic of the wasting syndrome. In this article, the endocrine manifestations of AIDS with a particular emphasis on neuroendocrine mechanisms will be reviewed, followed in each case by a discussion of clinical implications.

ISSN:1051-2144    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

&NA;Maternal aging has a profound affect on the reproductive capabilities of women. Because many women are delaying childbirth, there is increasing interest in the mechanisms attendant to the reproductive dysfunction that they encounter. One of the primary targets of aging is the oocyte, which exhibits high rates of chromosome mismanagement during meiosis as maternal age increases. It is unknown whether environmental factors or the intrinsic biology of the oocyte is responsible for problems in chromosome segregation. However, studies into the process of meiotic maturation of the human oocyte will improve our understanding of this important reproductive process. This chapter focuses briefly on several areas of current interest in the regulation of meiosis, including specific molecular and structural components that play key roles in this process.

ISSN:1051-2144    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

&NA;Subclinical hypothyroidism is defined by the presence of mild thyrotropin (TSH) elevation but normal blood free thyroxine and free triiodothyronine levels. The adjective “subclinical” seems awkward, if not inaccurate, given that it is arguable whether these patients are truly asymptomatic and in view of the support in the literature for a salutary effect of thyroid hormone therapy. In view of this and the evidence that the majority of such patients eventually evolve into overt thyroid failure, we propose that a more appropriate term is minimally symptomatic hypothyroidism (MSH). The most common causes of this syndrome are the same as those for overt hypothyroidism and include chronic autoimmune (Hashimoto's) thyroiditis, thyroid ablation with radioactive iodine, antithyroidal drugs, and thyroidectomy. Ideally, the diagnosis is best considered in an outpatient setting, because confounding factors in hospitalized patients, such as severe systemic illness and medications, can cause misleadingly elevated TSH levels. Although target organ dysfunction is not as evident as in overt hypothyroidism, well‐designed studies have reported subtle elevations in atherogenic lipoprotein fractions, suboptimal left ventricular function, and discrete neuropsychiatric abnormalities. In minimally symptomatic patients, it is important to reconcile optimal medical practice with the increasing demands of the current health care system for a judicious and cost‐effective approach to diagnosis and management. An initial clinical assessment for MSH could focus on identifying individuals vulnerable to thyroid disorders, such as patients with a family or past medical history of thyroid disease, patients with a goiter or history of recent pregnancy, patients taking medications that could interfere with thyroid function, or patients with hypercholesterolemia. TSH should be measured in all patients at risk, and measurement of thyroid antibody titers may be useful insofar as they confirm autoimmune thyroid disease and predict progression to frank hypothyroidism, especially in the geriatric population. We believe that there is reason to expect benefits from initiation of replacement therapy with levothyroxine, including relief of symptoms, improvement in lipid profiles and cardiovascular risk, and prevention of progression to overt hypothyroidism. Levothyroxine is given in the usual recommended doses, with an ultimate target dose of approximately 1.7 &mgr;g/kg, titrated accordingly to maintain serum TSH within the normal (measurable) range. Although still controversial, one recent article suggests that screening women older than age 35 every 5 years for MSH may be as cost‐effective as screening for breast cancer or hypertension.

ISSN:1051-2144    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Historical PerspectiveA novel group of orally active peptide and nonpeptide growth hormone (GH) secretagogues have significant potential for treatment of short stature, aging, hyperprolactinemia, and prolactinomas. In this manuscript, the experimental evidence providing the basis for postulating an endogenous ligand for growth hormone‐releasing peptide (GHRP) and mimics is reviewed. The background information supporting the hypothetical use of GHRP and growth hormone‐releasing factor also is provided. A multi‐tiered diagnostic test is recommended to differentiate various etiologies of GH secretory dysfunction. The observations gained from these diagnostic studies also may be applied to aging subjects. Also discussed is a hypothetical model using oral GH secretagogues in the treatment of hyperprolactinemia and prolactinomas. As additional investigations are carried out, the clinical applications for these novel secretagogues likely will be broadened.

ISSN:1051-2144    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

&NA;We describe two patients with bilateral testicular tumor associated with congenital adrenal hyperplasia resulting from 21‐hydroxylase deficiency. We conclude our analysis of these two patients by emphasizing the importance of appropriate treatment which, although unable to restore fertility, can avoid further growth of the adrenal rests.

ISSN:1051-2144    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

&NA;We describe a patient with an aggressive hypothalamic lymphoma whose clinical and biochemical features mimicked neurosarcoidosis. This case illustrates the point that although diagnostic tests might suggest neurosarcoidosis, biopsy confirmation is required.

ISSN:1051-2144    

出版商:OVID    

年代:1997

数据来源: OVID