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Psychological Factors in Endocrinology
Despite some of the early psychosomatic literature, there is no unique diabetic personality, but physicians who take care of diabetic patients attest to a close interrelationship between psy-chological factors and glucose control. There is conflicting evi-dence whether psychological factors directly affect the onset of diabetes. That psychological stress can adversely affect glucose control in diabetics seems expectable because the hormones of the stress response are part of the counterregulatory response to insulin. A number of studies have shown that glycemic control is poorer in those diabetic patients who have more perceived stress. As assessed by hemoglobin A1c, metabolic control was poorer in depressed children and in adult depressed type 1 but not type 2 diabetics. A recent meta-analysis of 24 studies concluded that depression consistently is associated with a small-to-moderate increase in hyperglycemia in both type 1 and type 2 diabetes (Lustman et al., 2000). Depression is associated with more dia-betic complications. Most such research has been retrospective or cross-sectional, leaving it unclear which came first – poor meta-bolic control and complications or the psychological factor – and what is the relationship between them.
When psychiatric illness antedates and adversely af-fects the course of diabetes, it may be mediated by noncompli-ance (diet, medication, activity, visits to the physician, self-care) (Ciechanowski et al., 2000) or by neurohumoral mechanisms. The adverse effects in diabetic control cannot all be attributed to noncompliance. Psychological stress administered under laboratory conditions can impair glucose control in both insu-lin-dependent and noninsulin-dependent diabetes. In insulin-dependent diabetes, this effect appears to be mediated by mental stress-induced insulin resistance.
Randomized controlled trials have demonstrated improve-ments in glucose control in diabetics receiving psychological interventions. Antidepressants are effective in the treatment of depression in diabetics, but can cause increases or decreases in blood glucose by themselves. Deterioration in glucose control in schizophrenic diabetics may be due to some of the newer antipsy-chotic drugs, but diabetes was a major problem for schizophrenics before their advent, presumably because of obesity (a side effect of almost every antipsychotic), unhealthy diet and poorer health care. Optimal management of diabetes requires a degree of orga-nization very difficult for most patients with schizophrenia.
It is well established that too little or too much thyroid hormone can result in disturbances in mood and activity. In the other di-rection, the effects of emotion and stress on thyroid function, although long a focus of interest, are less well established. Recent studies have supported stressful life events as a risk factor for Graves’ disease. Psychological stress may also be a result of less optimal control of hyperthyroidism.
Whereas there has been little well-substantiated evidence of the impact of psychological factors on thyroid disease, altera-tions in thyroid function or its hypothalamic–pituitary control have been demonstrated in relation to affective disorders, schizo-phrenia and post traumatic stress disorder. Depression has been most studied, revealing a variety of thyroid abnormalities, most frequently a relative increase in thyroxine without changes in the activated (triiodothyronine) and inactive (reverse triiodothyro-nine) forms and a blunting of the thyroid-stimulating hormone response to thyrotropin-releasing hormone. There is no agree-ment regarding the relationship between these endocrine changes and depressive pathophysiological processes, and it remains un-known whether depression modifies endocrine measures in clini-cal thyroid disease.
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