Phillip C. Owens

Postnatal disappearance of the pregnancy-associated reduced sensitivity of plasma cortisol to feedback inhibition.

We recently observed that the characteristic insensitivity of the pituitary-adrenal system in women to feedback inhibition during pregnancy persists for at least four days postnatally. We therefore examined women during the first five weeks after delivery to assess when the sensitivity of plasma cortisol to glucocorticoid inhibition returns to normal. Dexamethasone (DEXA, 1 mg) was ingested at 11 pm by normal healthy women, once between the 3rd and 27th postnatal days, and again on day 35. Blood plasma was collected at 4 pm on the following day for cortisol assay. Plasma cortisol levels (nmol/L, mean +/- sem [n]) after DEXA in the first two weeks (216 +/- 28, [47]) were higher (p less than 0.001) than in nonmedicated nonpregnant women (47.4 +/- 8.9 [12]) and were normal by the 35th day after delivery (41.7 +/- 4.8 [74]). A negative association was found between post-DEXA cortisol and time after delivery in the first 4 post-partum weeks (r = -0.46, p less than 0.001). The study confirms that insensitivity of plasma cortisol to feedback inhibition persists beyond normal pregnancy in a significant proportion of healthy women for two to three weeks, and is absent by the 5th postnatal week.

Peripartum Concentrations of Beta Endorphin and Cortisol and Maternal Mood States

Summary: Nineteen women were studied before, during and after labour by assessment of their mood using a variety of psychological tests and by measurement of their plasma concentrations of beta‐endorphin and Cortisol. Beta‐endorphin and Cortisol concentrations rose markedly during labour and were influenced by the type of analgesia used. A deterioration in cognitive performance between days 2 and 4 postpartum correlated positively with the fall in beta‐endorphin concentrations from those in labour to those on the fourth day postpartum. The women were more anxious and depressed at 38 weeks gestation than on days 1–4 postpartum and the elevation of mood on day 2 postpartum correlated with a measure of depression 8 weeks later. It is postulated that the phenomenon of postpartum blues is a reaction to the euphoria of delivery which in turn is a response to endorphin release during labour. Whilst these changes may have a role in promoting maternal‐infant attachment it is at the expense of maternal depression some weeks later.

Opioid peptides in blood and cerebrospinal fluid during acute stress

The opioid peptides beta-endorphin and [met]enkephalin are present in the peripheral circulation. Plasma beta-endorphin originates from the pituitary gland and its cosecretion with ACTH is stimulated by a variety of noxious stimuli. Although the adrenal medulla contains high concentrations of [met]enkephalin-containing polypeptides which are costored with catecholamines, and although the adrenal gland appears to secrete [met]enkephalin into the adrenal vein, the relative adrenal contribution to plasma [met]enkephalin appears to be negligible. Plasma concentrations of immunoreactive [met]enkephalin may be increased by insulin and by endotoxic shock, but they are not significantly altered by acute haemorrhagic stress nor by surgical stress. Thus blood plasma concentrations of beta-endorphin, but not of [met]enkephalin, are generally increased during acute stress. The physiological significance of endogenous opioids in the circulation is not known. It is unlikely that transient increases in the concentrations of opioid peptides in peripherally circulating blood modulate nociception, since the peptides do not enter ventricular cerebrospinal fluid in detectable amounts under these conditions. Recent evidence has raised the possibility that circulating opioids may be involved in regulating blood glucose and in activating the immune system. It is also possible that circulating beta-endorphin and related polypeptides have non-opioid actions on a variety of peripheral tissues.