10 Endocrine aspects of postnatal mental disorders

Abstract

Biological research in postnatal mental illness has only a short history and few encouraging data have yet emerged. The most promising positive findings are perhaps preliminary evidence for an increase of postnatal depression in women with postpartum thyroid dysfunction, some evidence for an enhanced sensitivity to changes in progesterone levels in postnatal depression, and the presence of an opioid peptide with unknown function in the cerebrospinal fluid of women with puerperal psychosis. Although steroid hormones are generally thought to be aetiologically relevant since they freely enter the brain and are known to interact with central monoamine neurotransmitter systems, attempts to demonstrate abnormal levels in postnatal disorders have been disappointing. An important reason for this outcome may be the usually employed approach of isolated hormone measurements. Ovarian steroid levels show marked interindividual variations. Thus significant between-group differences may only be obtained when large numbers of subjects are tested. Since only the unbound fraction can enter the brain, its measurement should be included in such studies. In the case of cortisol, single values are insufficient because of the pulsatile nature and the circadian pattern of its release. Thus serial sampling over 24 hours is more appropriate to detect secretory abnormalities. Measurements of circulating peptides are difficult to interpret since the amount reaching the brain is at best small. What is needed here are estimations of peptides in the cerebrospinal fluid which, however, pose ethical problems. Another explanation for the dearth of consistent positive data may be that women with postnatal mental disorders react to normal postnatal changes differently to women who remain well after childbirth. There is already evidence that patients at high risk of puerperal manic-depressive illness develop a hypersensitivity of central D2 receptors which may be related to the effects of oestrogen withdrawal on the function of DA systems. Further investigations of central neurotransmitter function are needed. In many ways postnatal mental disorders provide a unique opportunity for psychosomatic research since their onset can almost be predicted and follows an event which is associated with changes in many physiological systems. Results of recent neuropharmacological and behavioural investigations into the central effects of steroid and peptide hormones provide the basis for a multitude of pathogenetic hypotheses to be tested in postnatal mental disorders and research in this area may see exciting times ahead.