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9 recordsLinked to original sources
PubMed1986

Reduced activation and affinity of renin during pregnancy and oral contraception: determination of kinetic parameters by a fully autologous plasma renin assay.

In healthy normotensive pregnancy, a complex functional network develops between the cardiovascular system, the volume and composition of the extracellular fluid and the renin-angiotensin system (RAS). Cardiac output and heart rate increase, but blood pressure is reduced. The kidneys increase in size and both the glomerular filtration rate and renal blood flow increase early. Renal tubular water and sodium reabsorption is even more enhanced, so that the total body water of mother and foetus rises in the course of pregnancy by 6-8 litres. Plasma osmolality falls by about 10 mosm/kg. yet total body sodium increases by about 1 mol. Understandably, in the face of such complex fluid and pressure adjustments, data on the changes of the RAS in normal pregnancy are often contradictory. However, there is general agreement that the angiotensinogen and inactive renin in plasma are greatly raised. Most groups have also found a considerable increase in active renin. These changes could lead to higher rates of angiotensin I (AI) formation (and hence high circulating angiotensin II levels), with adverse consequences for mother and foetus. The high proportion of inactive renin may reflect a reduction in the rate of activation of prorenin in order to avoid these consequences. This reduction may involve kallikreins which have been listed amongst the putative in vivo activators of prorenin. Excessive AI formation in pregnancy could also be avoided by the production of functionally different renins or angiotensinogens. Such changes will be difficult to detect with assays which require addition of extraneous renin or angiotensinogen.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiovascular Physiological Phenomena↗
PubMed1990

Time-dependent alterations in lipid metabolism during treatment with low-dose oral contraceptives.

The effect of sex steroids on lipid metabolism depends on the type and dose of the compounds, the route of administration, and the duration of treatment. Therefore the composition of an oral contraceptive determines the resultant effect on lipids and lipoproteins. During 12 months of treatment, the effects of two oral contraceptives containing 30 micrograms of ethinyl estradiol and 150 micrograms of desogestrel (EE/DG) or 75 micrograms of gestodene (EE/GSD) on 19 serum parameters of lipid metabolism were followed in 11 women each. There was no change in total cholesterol and phospholipids. Total triglyceride levels were significantly elevated only by EE/GSD. After 3 and 6 months of intake of both preparations, a transitory increase in the triglyceride content of very low-density lipoprotein and low-density lipoprotein and a decrease in low-density lipoprotein-phospholipids was observed. After 12 months, very low-density lipoprotein cholesterol, very low-density lipoprotein phospholipids, and apolipoprotein B were significantly elevated, whereas very low-density lipoprotein triglycerides and all components of low-density lipoprotein were unchanged. Most of the components of high-density lipoprotein (HDL) were increased as a result of a rise in HDL3 and apolipoprotein A2, whereas HDL2 and apolipoprotein A1 were not altered. There was no significant difference between the effects of the two preparations, although those of EE/GSD were mostly more pronounced. The increase in high-density lipoprotein, very low-density lipoprotein, and total triglycerides reflects a slight preponderance of the effect of the estrogen component. Because low-density lipoprotein cholesterol and total cholesterol were not changed, treatment with both formulations is in all probability not associated with an elevated risk of atherosclerosis.

Adolescent↗
PubMed1990

Lipids, cardiovascular disease, and oral contraceptives: a practical perspective.

Figure 9 is an attempt to summate the influences of life-style on lipid parameters. Based on the work of Nikkila, it shows the source of the production of HDL and LDL, the factors that can affect these lipoprotein levels, and where in the cascade of lipoprotein metabolism these factors exert influence. The source of HDL production is the liver and the intestine. At this stage, diet, exercise, hormones, genetics, drugs, and certain disease states can affect HDL levels. Lecithin-cholesterol acyl transferase (LCAT) esterifies HDL-free cholesterol in plasma, and HDL3 is formed that in turn is transformed to HDL2. At the same time, VLDL from the gut and the liver will be converted, under the influence of LPL, to HDL2 and LDL. Thus HDL2 is being formed by the breakdown of VLDL and from the transformation of HDL3 to HDL2. Insulin, exercise, alcohol, fats, drugs, and diet affect lipoprotein lipase and consequently influence levels of LDL and HDL2 indirectly. Progestogens increase and estrogens decrease hepatic endothelial lipase, thus affecting the HDL2 concentration. It is at this point that combination OCs influence HDL2. The balance between estrogen and progestogen in a given contraceptive determines the extent and direction of HDL2 concentration. A separate pathway in the liver also catabolizes HDL2 and HDL3. LDL is generated partly from catabolism of VLDL and is partly secreted from the liver. The removal of LDL is mediated by receptors in both the liver and peripheral tissues. It is here that the Brown-Goldstein theory plays a major role. If LDL receptors are present in an insufficient number or are defective, then the C will accumulate and atherosclerosis may follow. Thus two key enzymes, LCAT and LPL, control the production of HDL2 and LDL, whereas a third enzyme, hepatic endothelial lipase, catabolizes HDL2.

Cardiovascular Diseases↗
PubMed1995

Contraceptive implant use among inner city teens.

PURPOSES: This study develops a clinical profile of urban teens who selected Norplant for contraception; determines which variables identify the subjects most likely to be compliant with the method; and determines the most common reasons for early termination of use. METHODS: Demographic and health history data and reasons for termination of use were collected prospectively for 122 inner city teens who received Norplant. Life table analysis and the Mantel-Haenszel procedure were used to investigate differences between Norplant retainers and terminators. RESULTS: The sample consisted of black and Hispanic teens between the ages of 13-19 years, the majority of whom had one or more children and were in school. One and two year retention rates were 71% and 62%. The highest removal rates occurred during the 3-6 month interval after insertion. A significant finding was that teens who have experienced induced abortion were more likely to retain Norplant. Common reasons for termination of use included general and social concerns, including pregnancy desire. CONCLUSIONS: Norplant retention rates for this teen sample were greater than the compliance rates reported for other conventional methods. Similar to noncompliance with oral contraceptives, discontinuance of the method was most likely to occur in the first 6 months of use. A history of induced abortion identifies those teens most likely to retain Norplant, suggesting that these teens might evaluate contraceptive risks and benefits differently than those with no abortion history. Pregnancy desire was a common reason for terminating Norplant use.

Adolescent↗
PubMed1975

Plasma dopamine-beta-hydroxylase activity in oral contraceptive hypertension.

A prospective study was undertaken to evaluate the relative contribution of changes in sympathetic nervous system activity, as reflected by changes in dopamine-beta-hydroxylase (DBH) activity, to the pathogenesis of oral contraceptive-induced hypertension. Precontraceptive and serial post contraceptive determinations of blood pressure, plasma renin activity (PRA), DBH activity, and changes in body weight were obtained in twelve control patients and forty-one oral contraceptive users. Forty-four percent of oral contraceptive users had increases in blood pressure but remained normotensive and 17% became frankly hypertensive. The precontraceptive and average post contraceptive levels of mean arterial pressure (MAP), PRA and DBH activity in each patient were compared using paired group analysis. Control patients (group I) exhibited no significant changes in these variables, while the patients with contraceptive-induced increases in MAP (groups III and IV) underwent significant, parallel increases in DBH activity. Finally, the linear regression of changes in MAP on the percent change in DBH activity was examined. The positive slopes in groups III and IV differed significantly from the negative slope of the controls (group I). The data have been interpreted to reflect an inappropriate oral contraceptive-induced stimulus to sympathetic nervous system activity, leading to increases in MAP in susceptible individuals.

Adult↗
PubMedDate not supplied

Triphasic pills: variability of endocrine parameters and of sex steroid-binding globulins.

A hundred and twenty healthy women who did not desire pregnancy were selected to check the effects of triphasic oral contraceptives on endocrine parameters and on plasma levels of steroid-binding proteins. Three groups of 40 women each were treated with 3 different pills containing different doses of ethynilestradiol in combination with noretistherone or levonorgestrel or gestodene, for a 6-month period. Serum concentrations of pituitary, ovarian and adrenal hormones, sex-hormone binding globulin and corticosteroid binding globulin were measured, basally and after the 6th cycle. Triiodothyronine and thyroxine were also tested. After 6 cycles the three oral contraceptives determined the inhibition of gonadotropins, ovarian steroids and Dehydroepiandrosterone Sulphate as well as an increase in Cortisol, triiodothyronine, thyroxine, sex hormone binding globulin and corticosteroid binding globulin. Prolactin levels did not vary. In the groups that receive the pills containing noretistherone, levonorgestrel and gestodene, sex hormone binding globulin increased by 138-136 and 156 per cent respectively, while corticosteroid binding globulin increased by 89-75 and 82 per cent respectively. The higher increase in sex hormone binding globulin, caused by gestodene-containing pill, testifies to the selectivity of this progestogen towards a lower androgenicity than norethisterone and levonorgestrel.

Adolescent↗
PubMed1983

Why do inadvertent pregnancies occur in oral contraceptive users? Effectiveness of oral contraceptive regimens and interfering factors.

Inadvertent pregnancies in combined pill users are not uncommon, and are usually due to errors of tablet taking. However, many factors may contribute to 'pill failure'. In this review the endocrine pharmacology of pill use and the changes reported with missed pills have been considered in detail. The influences of other factors including drug interactions have been reviewed and a series of recommendations made for reducing the risk of pregnancy in each of these circumstances.

Anti-Bacterial Agents↗
PubMedDate not supplied

Birth control discontinuance as a diffusion process.

This paper applies the diffusion of innovations model to the study of the birth control discontinuance of first-time users in the Dominican Republic. Two sets of factors are examined: social characteristics of the adopters are used to test Rogers's and Shoemaker's contention that discontinuers have more traditional values than continuers; and the adoption decision process is analyzed to identify the relationship of communication factors to discontinuance. Although number of children and experience of method problems were the major determinants of discontinuance, unfavorable information from friends and other birth control users was a significant factor. Rumor was found to have little effect on a women's decision to continue or discontinue.

Adult↗