Exposure to microgravity (weightlessness) is known to cause rapid bone and muscle losses. We have used the hind limb-suspended (HLS) rat model to simulate microgravity-induced musculoskeletal losses in order to assess resulting hormonal changes and to develop a novel pharmacological countermeasure. Previously, we demonstrated significant decreases in circulatory hormonal levels [serum thyroxin,...

INTRODUCTION Androgen decline in the aging man has become a topic of increasing clinical relevance worldwide, as the reduction in testosterone levels has been reported to be accompanied by loss of muscle mass, accumulation of central adiposity, impaired mobility and increase risk of bone fractures. Although well-established in studies conducted in developed countries, progressive decline in ser...

Seminal plasma (SP) plays an important role in the motility, viability and maintenance of the fertilizing capacity of mammalian spermatozoa. This study is the first on brown bear (Ursus arctos) SP components, and has two main objectives: 1) to define the SP composition in bear ejaculate and 2) to identify variations in SP composition in relation to high and low levels of testosterone in serum d...

BACKGROUND Some studies have provided evidence for a possible association between vitamin D and testosterone levels; however, the evidence from studies in Koreans is inconsistent. In addition, insufficient evidence is available to support an association between seasonal variations in vitamin D and testosterone levels in Koreans. Therefore, we aimed to investigate the association between vitamin...

introduction: thyroid hormones play an important role in the regulation of metabolism, maturity and reproduction. thyroid dysfunction affects almost all endocrine glands such as pituitary and testis. the aim of this study was to investigate alterations of testosterone and luteinizing hormone (lh) serum levels as well as weights of thyroid gland and testes in methimazole (mmi)-induced hypothyroi...

BACKGROUND Testosterone administration to hypogonadal men improves the metabolic syndrome. This study analyzed whether age, serum testosterone, body mass index/waist circumference, increment in testosterone values and C-reactive protein (CRP) predicted the outcome of testosterone administration. MATERIALS AND METHODS A total of 110 mainly elderly men, aged between 18 and 83 years (mean±SD=59....

BACKGROUND Concentrations of human tissue kallikreins (hKs), a group of 15 secreted serine proteases found in many tissues, are modulated by steroid hormones in cancer cell lines. To gain insight into in vivo kallikrein regulation we measured kallikrein concentrations in serum and urinary tissue in female-to-male transsexuals before and after testosterone administration. METHODS We collected ...

Differentiation between subtle changes in low serum testosterone concentrations, common in women and children, is not possible with current commercially available assays. The objectives of the study were to develop a method based on stable isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) with adequate sensitivity and specificity and to investigate the applicability ...

Introduction: Numerous studies have demonstrated that kisspeptin, a peptide from the KISS1 gene, plays an important role in regulating the secretion of gonadotropin releasing hormone (GnRH). Also, there is some evidence suggesting that kisspeptin can interact with other neuropeptides for the control of the reproductive axis. In the present study, we have investigated the effect of central admin...