Katz, Jonathan Richard; (2001) Production and interconversion of steroid hormones in obesity and polycystic ovary syndrome. Doctoral thesis (M.D), UCL (University College London).

Text Production_and_interconversion.pdf Download (4MB)

Abstract

This thesis examines alterations in the metabolism of steroid hormones in two conditions—obesity and polycystic ovarian syndrome (PCOS). Whilst few authors doubt that alterations in steroid hormone metabolism occur in obesity and PCOS, there is considerable debate in the literature as to the exact nature of these perturbations. The metabolism of two groups of steroid hormones—corticosteroids and sex steroids—is assessed in obesity and PCOS. Chapters 1 and 2 introduce the thesis and describe the methods, respectively. The initial study (Chapter 3) assesses the integrity of the hypothalamo-pituitary-adrenal axis (HPAA) in obesity. Some authors propose that a hyperactive HPAA gives rise to central obesity. Evidence is presented in favour of a hyperactive HPAA in centrally obese men. The equilibrium of the cortisol-cortisone shuttle in adipose tissue is investigated. An in vivo study of arteriovenous sampling is described in Chapter 4, demonstrating that subcutaneous abdominal adipose tissue produces cortisol from cortisone, accounting for 4% of daily cortisol production. Adipose tissue thus produces its own growth factor—cortisol—which may exacerbate obesity in a vicious cycle. Androstenedione conversion to testosterone in adipose tissue is said to account for 60% of testosterone production. Does peripheral testosterone production account for the hyperandrogenism seen in obese subjects with PCOS? In Chapter 5, total body fat testosterone production is calculated to be equal in PCOS and non-PCOS obese women, representing a lower proportion (4–10%) of systemic production than previously described. However, acute hyperinsulinaemia in the euglycaemic clamp increases peripheral production of testosterone (Chapter 6) without altering systemic testosterone levels (Chapter 7). This thesis extends scientific knowledge on abnormalities of steroid hormone metabolism in obesity and the role of adipose tissue as an endocrine organ.

Download activity - last month

Export as JSONXMLCSV

Download activity - last 12 months

Export as CSVXMLJSON

Downloads by country - last 12 months

Export as CSVJSONXML

Archive Staff Only

View Item