ISSN:1051-2144    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:1051-2144    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Since Corrigan and co-workers first reported the selective venous sampling from the inferior petrosal sinus in Cushing's disease in 1977, many modifications of this technique have been developed. In consequence, the bilateral simultaneous petrosal sinus sampling has been established and widely used. With this technique, a pituitary lesion is suggested when the central to peripheral (c/p) ratio of adrenocorticotropic hormone is greater than 1.5–2.5 (usually 2.0). An intersinus gradient of more than 1.4 indicates the lateralization of a microadenoma.However, false negative cases existed in 8–25% of examined subjects, mainly because of the dilution of pituitary blood with the blood of the other part of the cranium. In order to enhance the diagnostic accuracy, several authors recommended the corticotropin-releasing factor stimulation test during the sampling or simultaneous measurements of other pituitary hormones (usually prolactin).Based on this background information, we have developed the method of selective venous sampling directly from the cavernous sinus using the modern technology of intravascular surgery. This method provides sufficient c/p ratio (more than 10) for reliable diagnosis of Cushing's disease. The lateralization of microadenomas can be also estimated by the intercavernous gradients in all cases except for midline tumors.

ISSN:1051-2144    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

The capacity of the parathyroid glands to sense minute changes in the extracellular calcium concentration (Cao2+) is crucial for maintaining mineral ion homeostasis, but the mechanisms(s) by which parathyroid cells and other cell types detect and respond to changes in ambient calcium have remained obscure. Recent applications of molecular biological techniques have provided key insights into these mechanisms. A cDNA encoding a Cao2+-sensing receptor from bovine parathyroid has been isolated using expression cloning inXenopus laevisoocytes. The receptor has pharmacological properties nearly identical to those of the native receptor and, as in parathyroid cells, stimulates PLC in a G-protein-dependent fashion. The deduced amino acid sequence of the cloned receptor predicts a protein of Mr121 kD, with three principal structural domains: (1) a 613 amino acid aminoterminal portion with clusters of acidic residues possibly involved in binding Ca2+and other cationic ligands, (2) seven membrane-spanning helices characteristic of G-protein coupled receptors (GPR), and (3) a 222 amino acid cytoplasmic tail. Receptor transcripts are present in parathyroid as well as in thyroid, kidney, and brain. Because they show abnormal Cao2+-sensing in parathyroid and kidney, we investigated the hypercalcemic disorders, familial hypocalciuric hypercalcemia (FHH) and neonatal severe hyperparathyroidism (NSHPT) as possible candidate diseases with inherited abnormalities in the Cao2+-sensing receptor. Indeed, there proved to be mutations in the coding region of the receptor gene in affected members of 3 FHH families, including one homozygote with NSHPT, who had two abnormal alleles. A construct of the receptor incorporating one of these mutations had over a 90% reduction in its activity when expressed inXenopusoocytes. Thus, this Cao2+-sensing receptor is a member of the superfamily of GPRs, and inactivating mutations lead to extracellular Ca2+“resistance.” Furthermore, this receptor may mediate some of the long-recognized but poorly understood actions of extracellular calcium on the kidney and other cells, enabling calcium to act as an extracellular first messenger in addition to subserving its well-recognized role as an intracellular second messenger.

ISSN:1051-2144    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

A 33-year-old Caucasian male presented with unilateral gynecomastia after unilateral orchiectomy for a Leydig cell tumor. The serum estradiol (E2) level was elevated, the testosterone (T) level was normal, and the gonadotropin levels were high-normal. The patient underwent unilateral mastectomy for cosmetic purposes. Problems with mood and libido plus the development of gynecomastia in the contralateral breast caused him to seek further treatment. Testolactone (TL) at 400 mg/day afforded complete resolution of his symptoms and gynecomastia, both of which recurred when the drug was withdrawn and responded to resumption of therapy. The serum E2level initially fell during TL therapy but returned to pretreatment levels after 1 month. The serum T, however, doubled during treatment periods, increasing the androgen/estrogen ratio. Testolactone appears to effectively treat this condition by raising the androgen/estrogen ratio without lowering absolute E2levels.

ISSN:1051-2144    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Hypoglycemia of a degree sufficient to cause cerebral dysfunction does not occur in healthy people. Only if counter-regulatory defenses fail will blood glucose levels fall to a level that results in abnormalities in brain function: drowsiness, confusion, and, ultimately, coma. This review will explore the causes of hypoglycemia, the underlying mechanisms, and useful strategies for avoiding this serious complication in the diabetic subject.

ISSN:1051-2144    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

In 1938, Dr. Henry H. Turner wrote: “the triad, infantilism, webbing of the neck, and deformity of the elbow (cubitus valgus), occurring in the same individual is unusual and continued, saying that it is sufficiently interesting to warrant this report These are the first words describing the genetic syndrome that today bears his name. Turner syndrome is now recognized in 1 of 2,000 live-born phenotypic girls and may be present in 1 of 15 spontaneous abortions. It is a form of mild skeletal dysplasia with short stature its primary manifestation and several other associated defects, a number of them secondary toin uterodeformations, and an endocrine disorder, consisting mainly of sexual infantilism caused by premature ovarian failure. All girls with Turner syndrome have an abnormal sex-chromosomal constitution that ranges from simple monosomy of the X chromosome (45,X karyotype) to complex cytogenetic aberrations involving the XX chromosomal pair (46.XX karyotype with deletions, translocations, inversions, and/or ring formations of the X chromosomic material). To date, the molecular genetics of the syndrome have not been elucidated, despite recent advances such as the cloning of the sex-determining gene SRY and its counterparts on chromosome X, SOX-genes. The phenotype of Turner syndrome is the result of a complex interaction of thein uteroand post natal expression of a number of genes located on the X chromosome responsible for sex-determination and function, final height, skeletal maturation, and development of other structures of mesenchymal origin. In this review, we discuss Turner syndrome from the aspect of the clinician geneticist, endocrinologist, and general practitioner.

ISSN:1051-2144    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

An indisputable physiological feature of anterior pituitary hormone secretion is a pulsatile mode of signaling. The temporally pulsatile nature of anterior pituitary hormone release is endowed by episodicity of neuronal activation in hypothalamic control centers, which convey an intermittent stimulatory and/or inhibitory signal to responsive anterior pituitary cells. The anterior pituitary gland in turn responds with bursts of hormone secretion into the bloodstream, and thereby commands remote target tissues in an unique temporally organized fashion. In the case of the gonadotropic (LH and FSH) axis in men and women and in pubertal children, the intermittency of hypothalamic GnRH's stimulation of gonado-trope cells is a critical determinant of sustained physiological function and is an absolute prerequisite to reproductive capability. Moreover, a host of pathophysiological derangements in various clinical states can be marked by disruption of the otherwise coordinated pulsatile release of gonadotropic hormones. Similarly, profound alterations in the burst-like mode of GH secretion occur throughout the human life span, and are typified by striking gender differences. Moreover, like LH, the pulsatile GH signal is profoundly modified by age (including changes within the first day of life and in adolescence, young adulthood, and older age), differences in body composition, degree of physical fitness, alterations in sleep and nutrient intake, and pathological disturbances in renal and hepatic function, among other conditions. Other neuroendocrine axes such as the corticotropic (ACTH) and lactotropic systems also manifest distinct physiological regulation of the burst-like mode of hormone secretion, and evince striking disturbances in conditions of disease. Importantly, because the frequency and amplitude of hormone secretory bursts are jointly controlled by hypothalamic (neuronal) effector pathways and systemic negative and positive feedback, an understanding of neuroendocrine pathophysiology offers unique insights into the brain's regulation of the anterior pituitary gland and the pituitary gland's susceptibility to feedback influences from peripheral target tissues. Here I review some of the salient recent concepts and developments in neuroendocrinology with a particular emphasis on physiological regulation and pathophysiological disruption of the pulsatile mode of LH secretion in girls, boys, women, and men

ISSN:1051-2144    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:1051-2144    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Congenital hypothyroidism, present in 1:4000 newborns, is one of the most common preventable causes of mental retardation. Screening programs, now routine in all 50 states, Canada, and most of the developed world, have been immensely successful in detection and early treatment of affected infants. Diagnostic studies show thyroid dysgenesis to be the most common etiology worldwide, with ectopic glands accounting for the majority of dysgenetic cases. Other etiologies include hereditary defects in thyroxine synthesis, hypopituitary hypothyroidism, and transplacental passage of maternal thyrotropin receptor blocking antibodies; the latter condition is usually associated with transient hypothyroidism. Many programs report good psychometric outcomes, with IQs similar to control groups. Some, however, report slightly lower IQs, particularly in the most severely affected infants. These IQ differences may result from the effects of fetal hypothyroidism, neonatal hypothyroidism that occurs between delivery and the restoration of euthyroid-ism with therapy, or suboptimal treatment in the first 2 years of life. Studies show that approximately one-third of maternal thyroid hormone crosses the placenta and may partially protect the hypothyroid fetus. It is therefore important that hypothyroid women are treated optimally during pregnancy. It is equally important that treatment of the newborn raise the serum T4> 10 μg/dL as rapidly as possible, using a starting dose of 10–15 mcg/kg/day. Careful monitoring to assure proper dosing and compliance in the first 2 years is also important to neurologic outcome. The future may include screening of women of child-bearing age for hypothyroidism and some way to screen and treat the hypothyroid fetus.

ISSN:1051-2144    

出版商:OVID    

年代:1994

数据来源: OVID