It was decades later that the secret behind this spectacular success became known. The East German Sports Federation had, with the help of the Stasi, used Performance Enhancing Drugs or PEDs to ensure that their athletes gained international recognition by winning the Olympic events. This systematic plan had been initiated in 1974 as a means to guarantee international glory through the achievement of gold medals at the prestigious sporting event. Oral- Turinabol , a testosterone derivative was used extensively to improve muscle mass and cut down recovery time. This allowed the German athletes to train harder and longer than other world athletes.
AB - The characterization of the superfamily of nuclear receptors, in particular the steroid/retinoid/thyroid hormone receptors, has resulted in a more complete understanding of how a repertoire of hormonally and nutritionally derived lipophilic ligands controls cell functions to effect development and homeostasis. As transducers of hormonal signaling in the nucleus, this superfamily of DNA-binding proteins appears to represent a crucial link in the emergence of multicellular organisms. Because nuclear receptors bind and are conformationally activated by a chemically diverse array of ligands, yet are closely related in general structure, they present an intriguing example of paralogous evolution. It is hypothesized that an ancient prototype receptor evolved into an intricate set of dimerizing isoforms, capable of recognizing an ensemble of hormone-responsive element motifs in DNA, and exerting ligand-directed combinatorial control of gene expression. The effector domains of nuclear receptors mediate transcriptional activation by recruiting coregulatory multisubunit complexes that remodel chromatin, target the initiation site, and stabilize the RNA polymerase II machinery for repeated rounds of transcription of the regulated gene. Because some nuclear receptors also function in gene repression, while others are constitutive activators, this superfamily of proteins provides a number of avenues for investigating hormonal regulation of gene expression. This review surveys briefly the latest findings in the nuclear receptor field and identifies particular areas where future studies should be fruitful.
The secretion of hypothalamic, pituitary, and target tissue hormones is under tight regulatory control by a series of feedback and feed- forward loops. This complexity can be demonstrated using the growth hormone (GH) regulatory system as an example. The stimulatory substance growth hormone releasing hormone (GHRH) and the inhibitory substance somatostatin (SS) both products of the hypothalamus, control pituitary GH secretion. Somatostatin is also called growth hormone-inhibiting hormone (GHIH). Under the influence of GHRH, growth hormone is released into the systemic circulation, causing the target tissue to secrete insulin-like growth factor-1, IGF-1. Growth hormone also has other more direct metabolic effects; it is both hyperglycemic and lipolytic. The principal source of systemic IGF-1 is the liver, although most other tissues secrete and contribute to systemic IGF-1. Liver IGF-1 is considered to be the principal regulator of tissue growth. In particular, the IGF-1 secreted by the liver is believed to synchronize growth throughout the body, resulting in a homeostatic balance of tissue size and mass. IGF-1 secreted by peripheral tissues is generally considered to be autocrine or paracrine in its biological action.