A review of 144 published studies of the relationship between socioeconomic status (SES) and obesity reveals a strong inverse relationship among women in developed societies. The relationship is inconsistent for men and children in developed societies. In developing societies, however, a strong direct relationship exists between SES and obesity among men, women, and children. A review of social attitudes toward obesity and thinness reveals values congruent with the distribution of obesity by SES in different societies. Several variables may mediate the influence of attitudes toward obesity and thinness among women in developed societies that result in the inverse relationship between SES and obesity. They include dietary restraint, physical activity, social mobility, and inheritance.

Socioeconomic Status and Obesity: A Review of the Literature

Most aging individuals die from atherosclerosis, cancer, or dementia; but in the oldest old, loss of muscle strength resulting in frailty is the limiting factor for an individual's chances of living an independent life until death. Three hormonal systems show decreasing circulating hormone concentrations during normal aging: (i) estrogen (in menopause) and testosterone (in andropause), (ii) dehydroepiandrosterone and its sulphate (in adrenopause), and (iii) the growth hormone/insulin-like growth factor I axis (in somatopause). Physical changes during aging have been considered physiologic, but there is evidence that some of these changes are related to this decline in hormonal activity. Hormone replacement strategies have been developed, but many of their aspects remain controversial, and increasing blood hormone levels in aging individuals to those found during mid-adult life has not been uniformly proven to be safe and of benefit.

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The Endocrinology of Aging

The heart is a major target organ for thyroid hormone action, and marked changes occur in cardiac function in patients with hypo- or hyperthyroidism. T(3)-induced changes in cardiac function can result from direct or indirect T(3) effects. Direct effects result from T(3) action in the heart itself and are mediated by nuclear or extranuclear mechanisms. Extranuclear T(3) effects, which occur independent of nuclear T(3) receptor binding and increases in protein synthesis, influence primarily the transport of amino acids, sugars, and calcium across the cell membrane. Nuclear T(3) effects are mediated by the binding of T(3) to specific nuclear receptor proteins, which results in increased transcription of T(3)-responsive cardiac genes. The T(3) receptor is a member of the ligand-activated transcription factor family and is encoded by cellular erythroblastosis A (c-erb A) genes. T(3) also leads to an increase in the speed of diastolic relaxation, which is caused by the more efficient pumping of the calcium ATPase of the sarcoplasmic reticulum. This T(3) effect results from T(3)-induced increases in the level of the mRNA coding for the sarcoplasmic reticulum calcium ATPase protein, leading to an increased number of calcium ATPase pump units in the sarcoplasmic reticulum.

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Thyroid Hormone Action in the Heart

In the 1980s the development of the doubly labelled water (DLW) technique made it possible to determine the validity of dietary assessment methods using external, independent markers of intake in free-living populations. Since then, the accuracy of self-reported energy intake (EI) has been questioned on a number of occasions as under-reporting has been found to be prevalent in many different populations. This paper is a review of investigations using the DLW technique in conjunction with self-reported EI measures in groups including adults, children and adolescents, obese persons, athletes, military personnel and trekking explorers. In studies where a person other than the subject is responsible for recording dietary intake, such as parents of young children, EI generally corresponds to DLW determined energy expenditure. However, in instances where the subjects themselves report their intake, EI is generally under-reported when compared with energy expenditure. It was originally believed that this phenomenon of under-reporting was linked to increased adiposity and body size, however, it is now apparent that other factors, such as dietary restraint and socio-economic status, are also involved. This paper therefore aims to present a more comprehensive picture of under-reporting by tying in the findings of many DLW studies with other studies focusing particularly on the characteristics and mechanisms for under-reporting. Awareness of these characteristics and mechanisms will enable researchers to obtain more accurate self-reports of EI using all dietary recording techniques.

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The validity of self-reported energy intake as determined using the doubly labelled water technique.

To determine whether the elevated plasma renin activity in some cases of mild essential hypertension expresses sympathetic-nervous-system over-activity, we compared indexes of sympathetic activity in 16 patients with mild high-renin essential hypertension, 15 hypertensive patients with normal plasma renin activity and 20 normal subjects. Patients with elevated activity exhibited a raised plasma norepinephrine concentration (P less than 0.05), a greater fall in cardiac output with cardiac beta-adrenergic blockade by intravenous propranolol (P less than 0.01), reduction in total peripheral vascular resistance with alpha-adrenergic blockade produced by intravenous phentolamine (P less than 0.01), and reduction to normal of blood pressure by "total" autonomic blockade (atropine, propranolol and phentolamine). On psychometric testing, patients with high-renin hypertension, but not those with normal plasma renin activity, exhibited suppressed hostility (P less than 0.01), a behavioral pattern linked to increased sympathetic activity. The hypertension in these patients with high renin activity is neurogenic and possibly psychosomatic in origin.

Mild high-renin essential hypertension. Neurogenic human hypertension?

Hypertensive patients with low plasma renin activity are suspected of having mineralocorticoid excess. We treated 26 hypertensive patients with the mineralocorticoid antagonist, spironolactone, 200 mg daily, and 25 patients with hydrochlorothiazide, 100 mg daily, for 12 weeks. Patients with low renin activity (below 250 ng/100 ml, 10 mEq sodium diet, upright position) and low normal renin activity (250 to 400 ng/100 ml) responded to both drugs with a significantly larger fall in blood pressure than was achieved by patients with renin activity above 400 ng/100 ml. Fall in blood pressure was related to the initial weight loss induced by spironolactone (r =.51), but was not related to the weight loss induced by hydrochlorothiazide. Both spironolactone and hydrochlorothiazide are more effective in reducing blood pressure in patients with low and low-normal renin activity than in other hypertensive patients.

Spironolactone and hydrochlorothiazide in essential hypertension. Blood pressure response and plasma renin activity.

Obesity and caloric intake: The national Health and Nutrition Examination Survey of 1971–1975 (HANES I)

Bone mineral density in postmenopausal women treated with L-thyroxine.

The cause of the suppression of plasma renin activity (PRA) in many patients with essential hypertension and normal aldosterone excretion is unknown. Since mineralocorticoid excess can lower PRA, we attempted to evaluate the activity of salt-retaining hormones in these patients by measuring the salivary Na/K ratio. The median Na/K ratio in 20 hypertensive patients with suppressed PRA and normal or low aldosterone excretion was 0.71. This was significantly lower than the median of 1.38 in 29 normal subjects and the median of 1.05 in 15 hypertensive patients with normal PRA. Excess dietary intake of salt is a possible cause of PRA suppression in these patients, but our findings indicate that high rather than low Na/K ratios would be expected if this were present. On the other hand, both the salivary electrolyte changes and the suppression of PRA are consistent with the hypothesis that mineralocorticoid excess is present in these patients, despite the failure to demonstrate elevated excretion of aldosterone.

Salivary Sodium-Potassium Ratio and Plasma Renin Activity in Hypertension

Excerpt At a time when 57 cents of each federal health care dollar is being spent on care of the elderly, the study of aging has moved to a position of high priority in medical research. Endocrinol...

E. Victor Adlin

Papers

Spironolactone and hydrochlorothiazide in essential hypertension. Blood pressure response and plasma renin activity.

Obesity and caloric intake: The national Health and Nutrition Examination Survey of 1971–1975 (HANES I)

Bone mineral density in postmenopausal women treated with L-thyroxine.

Salivary Sodium-Potassium Ratio and Plasma Renin Activity in Hypertension

Endocrine Aspects of Aging