Sex steroid hormones and brain function: PET imaging as a tool for research

Abstract

Sex steroid hormones are major regulators of sexual characteristic among species. These hormones, however, are also produced in the brain. Steroidal hormone-mediated signaling via the corresponding hormone receptors can influence brain function at a cellular level and thus affect behavior and higher brain functions. Altered steroid hormone signaling has been associated with psychiatric disorders, such as anxiety and depression. Neurosteroids are also thought to have a neuroprotective effect in neurodegenerative diseases So far, the role of steroid hormone receptors in physiological and pathological conditions have mainly been investigated post-mortem on animal or human brain tissues. To study the dynamic interplay between sex steroids, their receptors, brain function and behavior in psychiatric and neurological disorders in a longitudinal manner, however, noninvasive techniques are needed. Positron emission tomography (PET) is a noninvasive imaging tool to quantitatively investigate a variety of physiological and biochemical parameters in-vivo. PET uses radiotracers aimed at a specific target (e.g. receptor, enzyme, transporter) to visualize the processes of interest. In this review, we discuss the current status of the use of PET imaging for studying sex steroid hormones in the brain. So far, PET has mainly been investigated as a tool to measure (changes in) sex hormone receptor expression in the brain, to measure a key enzyme in the steroid synthesis pathway (aromatase) and to evaluate the effects of hormonal treatment by imaging specific down-stream processes in the brain. Although validated radiotracers for a number of targets are still warranted, PET can already be a useful technique for steroid hormone research and facilitate the translation of interesting findings in animal studies to clinical trials in patients.

This article is protected by copyright. All rights reserved.

http://ift.tt/2yo4fe3