Opioid control of gonadotrophin secretion in humans

Hypothalamus-pituitary-axis (HPA) is constantly under the modulatory effect of many substances, such as neurotransmitters, neuromodulators and steroid hormones. Recently, the involvement of endogenous opioid peptides (EOP) in the control of the neuroendocrine mechanism modulating gonadotrophin secretion has been supported by several authors. It has been demonstrated that acute morphine administration decreases luteinizing hormone (LH) plasma levels and this is due to an inhibitory modulation on gonadotrophin releasing hormone discharge from the hypothalamic neurons. EOP are usually increased by stressant situations. In stress-induced amenorrhoea, the presence of low LH plasma levels and an abnormal LH pulsatile secretion has been related to an increased opioid activity, thus supporting the integrative role of opioids between hormonal and neuronal afferences of brain.