Biomedical subjects

T A Abdu

Publications and source records attributed to T A Abdu.

6 recordsLinked to original sources

PubMed2001

Endothelial dysfunction in endocrine disease.

In addition to diabetes mellitus and obesity, acromegaly, Cushing's syndrome, hypopituitarism, hypo- and hyperthyroidism, hyperparathyroidism and polycystic ovary syndrome are associated with either increased mortality from, or increased prevalence of, cardiovascular disease (CVD). Recently, endothelial dysfunction has been identified as an early marker of CVD and has been shown to predict future coronary artery disease, before atherosclerotic changes appear in arteries. Thus, measurement of endothelial function might identify at-risk individuals early and be a useful means of assessing response to treatment aimed at reducing long-term morbidity and/or mortality from CVD. Such studies are being undertaken in hypopituitarism and other endocrinopathies, and are reviewed herein. Endothelial function in large vessels can be measured noninvasively by ultrasound measurement of flow-mediated endothelium-dependent dilation (FMD). Serum markers of endothelial function, such as von Willebrand's factor, thrombomodulin, E-selectin and intercellular adhesion molecule 1, could be increased and be useful for evaluation of treatment, because they correlate inversely with FMD.

Acromegaly↗

PubMed2001

Coronary risk in growth hormone deficient hypopituitary adults: increased predicted risk is due largely to lipid profile abnormalities.

BACKGROUND: Hypopituitarism in adults is associated with increased vascular mortality, which has been attributed to GH deficiency. OBJECTIVE: To compare the lipid profile and coronary risk predicted by the Framingham Heart Study equation in GH-deficient hypopituitary patients and healthy age and gender-matched controls. DESIGN: A cross-sectional observational study. METHODS: We studied 50 adult-onset growth hormone deficient hypopituitary patients (23F, 27M), on appropriate conventional hormone replacement and 45 controls (22F, 23M) matched for age, gender and smoking habit. The subjects (age range 30-75 years) were free from diabetes, hypertension, ischaemic heart disease (IHD) and peripheral vascular disease. All hypogonadal male patients were on testosterone replacement therapy. A similar proportion of female patients (8/23) and controls (7/22) were on HRT. Body mass index (BMI), waist-hip ratio (WHR) and blood pressure were recorded. After an overnight fast blood glucose, total-cholesterol, triglycerides, HDL-cholesterol, apolipoproteins A-I, B and Lp (a) were measured. Coronary risk was calculated for each individual from age, gender, systolic blood pressure, total and HDL cholesterol, smoking habit and presence of diabetes and left ventricular hypertrophy using the Framingham equation. RESULTS: BMI and WHR were significantly increased in GHD hypopituitary adults of both sexes, but to a greater extent in females. Triglycerides were elevated in both sexes. Total and LDL-cholesterol were increased in both sexes (significantly only in males), and HDL cholesterol and apo A-I were lower (significantly only in females). The reduction in HDL cholesterol was correlated negatively with adiposity (BMI), particularly when centrally distributed (WHR) in patients and controls. LDL cholesterol did not correlate to adiposity but higher levels were present in GH-deficient subjects. The total to HDL cholesterol ratio was significantly increased in patients of both genders (P = 0.002). There were no differences in the apolipoproteins B and Lp(a) between patients and controls. Absolute risk (mean +/- SEM) of a fatal or non-fatal coronary event during the next 5 years was significantly greater in GHD hypopituitary patients than control subjects (4.82 +/- 0.73% vs. 2.94 +/- 0.53, P = 0.04). Cardiovascular risk relative to the local population (RR) was significantly higher in GHD hypopituitary adults (RR = 1.43 CL 1.06-1.80, P = 0.011) but not in the control group (1.08 CL 0.59-1.6). When divided by gender, RR for male patients was not increased (1.14 CL 0.83-1.45, P = 0.096). However, female patients had significantly higher RR (1.7 CL 1.05-2.5, P = 0.048). The RR for male and female controls was not different from the local population. CONCLUSION: Changes in lipid levels help to explain the results from risk factor modelling which show increased coronary risk in growth hormone deficient hypopituitary patients, particularly females. The abnormal lipid profile is characterized in both genders by an increase in the total to HDL ratio [corrected], an important parameter in the Framingham equation. The lipid abnormalities conferring increased risk is related to growth hormone deficiency either directly (LDL) or indirectly through increased central obesity (HDL) [corrected]. Adverse calculated coronary risk might provide a new objective indication for consideration of GH replacement therapy in adults.

Adult↗

PubMed2001

Plasma homocysteine is not a major risk factor for vascular disease in growth hormone deficient adults.

OBJECTIVE: Several cardiovascular risk factors have been investigated in patients with adult growth hormone deficiency (GHD) to explain the observed increase in vascular mortality. Plasma homocysteine concentration has been identified recently as an independent risk factor for atherosclerosis. We wished to determine whether plasma homocysteine contributes to cardiovascular risk in adult GHD. METHOD: Plasma homocysteine was measured by fluorescence polarization immunoassay in 45 GH-deficient adults on stable conventional hormone replacement (25M, 20F), age range 23-76 years, and compared with 55 matched controls (30M, 25F), age range 21-77 years. All subjects were free from clinical hypertension, diabetes, ischaemic heart disease and peripheral vascular disease. Blood pressure, body mass index and waist hip ratio were recorded. Serum creatinine and fasting lipids were measured. Serum vitamin B12 and folate levels, important cofactors in the homocysteine metabolic pathways, were also measured. RESULTS: Homocysteine levels were not different in patients and controls (9.75 [7.8-11.6] micromol/l vs. 9.65 [8.3-11.5] micromol/l, respectively, P = 0.88). Serum vitamin B12 was also not different (320.5 [262.0-427.5] pmol/l vs. 313.5 [277.0-460.5] pmol/l, respectively, P = 0.77). Serum folate levels were significantly lower in the patient group (7.05 [5.12-8.27] ng/ml vs. 7.80 [6.52-10.60] ng/ml, respectively, P = 0.03). When separated by gender, in males folate was not significantly different between patients and controls 7.05 [5.17-9.19] vs. 7.65 [6.15-10.22], P = 0.264, whereas in females, folate was significantly lower in patients at 7.05 [4.57-7.75] compared to controls at 8.4 [6.60-12.20], P = 0.01. CONCLUSION: Plasma homocysteine levels are not significantly elevated in GH-deficient adults and are unlikely to be a major risk factor for vascular disease in these individuals.

Adult↗

PubMed2001

Biochemical and biophysical markers of endothelial dysfunction in adults with hypopituitarism and severe GH deficiency.

Adult hypopituitarism is known to be associated with reduced life expectancy related to excess vascular events, and endothelial dysfunction is present in patients with this condition. We studied the relationship between biophysical and biochemical markers of endothelial dysfunction, including E-selectin, intercellular cell adhesion molecule-1, von Willebrand factor, and thrombomodulin in 52 adult patients with hypopituitarism and severe GH deficiency (<2 ng/ml on provocative testing) compared with 54 age-, sex-, and smoking-matched normal controls. We also examined endothelium-dependent dilatation of the brachial artery to postischemic occlusion and carotid artery morphology (intima-media thickness) by high-resolution ultrasonography. The patients were stable on conventional hormone replacement therapy but not on GH therapy, and none of the subjects had a known risk factor for vascular disease. Levels of E-selectin [57 +/- 3 vs. 49 +/- 2 ng/ml (mean +/- SEM)] (P < 0.043), intercellular cell adhesion molecule-1 (308 +/- 11 vs. 266 +/- 10 ng/ml) (P < 0.001), thrombomodulin (49 +/- 3 vs. 35 +/- 2 ng/ml) (P < 0.001), and von Willebrand factor (132 +/- 7% vs. 105 +/- 5%) (P < 0.004) were significantly higher in patients than in controls. Brachial artery endothelium-dependent dilatation was significantly lower in patients than in controls [4.7% (0.00-9.77) vs. 10.5% (6.4-16.2) (median, interquartile range)] (P < 0.001). This difference in endothelium-dependent dilatation was more marked in female patients than in controls (P < 0.003), although it disappeared when estrogen-sufficient female patients were compared with controls (P = 0.31). However, the female patients who were not replaced with estrogen continued to show a striking difference compared with estrogen-deficient control females (P < 0.004). There was no difference in carotid intima-media thickness between patients of either sex and controls. On univariate analysis, brachial artery endothelium-dependent dilatation correlated inversely with intercellular cell adhesion molecule-1 (r = -0.225, P < 0.033). Intercellular cell adhesion molecule-1 correlated positively with E-selectin (r = 0.466, P < 0.0001) and negatively with IGF-I (r = -0.238, P < 0.016). E-selectin correlated with thrombomodulin (r = 0.215, P < 0.034) and von Willebrand factor (r = 0.218, P < 0.03) and negatively with IGF-I (r = -0.255, P < 009). Thrombomodulin correlated positively with von Willebrand factor (r = 0.422, P < 0.0001) and inversely with IGF-I (r = -0.266, P < 0.008). These correlations persisted after correction for age, sex, body mass index, and waist to hip ratio, with the exception of IGF-I, which now correlated with thrombomodulin only. These results confirm significant endothelial dysfunction in hypopituitarism and provide insight into the relationship of biochemical and biophysical markers of early atherosclerosis in hypopituitary GH-deficient adults. The negative correlation of IGF-I with some biochemical markers of endothelial dysfunction and the predictive nature of GH deficiency in stepwise regression analysis in this study supports the hypothesis that GH deficiency may play a role in these abnormalities. Future studies will determine whether GH treatment can reverse these abnormalities. Furthermore, the more significant endothelium-dependent dilatation abnormality in the female estrogen-deficient subjects compared with those who were estrogen replete suggests that estrogen replacement in these patients is a crucial element in protecting against vascular disease.

Adult↗

PubMed2001

Hypopituitarism and atherosclerosis.

In the last decade, retrospective cohort data has provided evidence of premature atherosclerosis in patients with hypopituitarism which may account for the recently observed increased death rate from vascular events in these patients. The exact mechanism(s) for such propensity to atherosclerotic vascular disease is not yet completely clear. It is possible that hormonal factors may be the initiating mechanisms with subsequent secondary metabolic abnormalities acting as risk factors for development of atherosclerosis. This seems to be more evident in female hypopituitary patients compared with their male counterparts. Female patients have higher frequency and more pronounced abnormalities of various risk factors as well as surrogate markers of early vascular disease. This may explain why morbidity and mortality in women is in excess of men in retrospective epidemiological studies. Addressing abnormal hormonal factors, especially in females, is a primary objective in managing these patients both in the clinical arena as well as in trials designed to reduce the risk of atherosclerotic vascular disease in these patients. While short-term growth hormone treatment may ameliorate some of the vascular risk factors and improve endothelial function, it remains to be shown whether this translates into long-term reduction in morbidity and mortality from vascular, especially cerebrovascular, disease.

Adult↗

PubMed1999

Comparison of the low dose short synacthen test (1 microg), the conventional dose short synacthen test (250 microg), and the insulin tolerance test for assessment of the hypothalamo-pituitary-adrenal axis in patients with pituitary disease.

There is still uncertainty about what is the most appropriate test for assessment of the integrity of the hypothalamo-pituitary-adrenal (HPA) axis. Many advocate the insulin tolerance test (ITT), but this is unpleasant and resource intensive, and may occasionally give misleading results. The conventional [250 microg tetracosactrin, ACTH-(1-24)] short synacthen test (SST) has been used as a simple alternative to the ITT, but it has produced some falsely reassuring results with potentially serious consequences. A low dose [1 microg tetracosactrin, ACTH-(1-24)] short synacthen test (LDSST) has recently been advocated as a more reliable and safer alternative to ITT. Some studies, however, have failed to demonstrate any difference between SST and LDSST. The purpose of this study was to assess the clinical usefulness of LDSST compared to SST and ITT in patients with pituitary disease. We studied 64 patients with suspected or proven pituitary disease. All patients underwent SST and LDSST. Forty-two patients underwent ITT. There was a high correlation between the ITT and LDSST peak cortisol responses (r = 0.89; P < 0.0001), the ITT and SST 30 min cortisol levels (r = 0.83; P < 0.0001), and the LDSST peak cortisol response and the SST 30 min cortisol level (r = 0.85; P < 0.0001). In the LDSST, all but six patients achieved maximal cortisol response by 30 min. A plasma cortisol cut-off of 600 nmol/L is more helpful than 500 nmol/L for clinical decision-making using either the SST 30 min cortisol level or the LDSST peak cortisol response. The sensitivity of the LDSST was 100% (cortisol response of >600 nmol/L indicates intact HPA axis), with no falsely reassuring results. SST (pass cortisol level, >600 nmol/L) was less sensitive than LDSST, it produced 2 of 64 (3%) falsely reassuring results. Even the ITT (pass cortisol level, >500 nmol/L) failed to identify one patient with clinically evident cortisol deficiency. The results of this study indicate that both SST and LDSST, at a cortisol cut-off of 600 nmol/L, are safe for the purpose of clinical decision-making with regard to steroid replacement therapy in patients with pituitary disease. As the LDSST produced no falsely reassuring decisions, we suggest that this could replace the SST and ITT for initial evaluation of the HPA axis in patients with pituitary disease. We suggest administering 1 microg tetracosactrin, i.v., with sampling at 0, 20, and 30 min.

Adult↗