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Biomedical subjects

B P Hamilton

Publications and source records attributed to B P Hamilton.

At least 55 records · Page 3Linked to original sources
PubMed1982

Adrenal vein epinephrine levels: a useful aid in venous sampling for primary aldosteronism.

We evaluated the usefulness of adrenal vein epinephrine levels as an indicator of adrenal venous dilution in seven patients with primary aldosteronism who had venous sampling. In six patients adrenal vein epinephrine levels greater than 1500 pg/mL confirmed that relatively undiluted adrenal efflux had been obtained. In another patient a low value of left adrenal vein epinephrine indicated that the sample was markedly diluted with nonadrenal blood. Measurement of epinephrine levels appears to be a useful tool for verifying successful venous sampling, particularly when cortisol and aldosterone levels from the same adrenal vein are not elevated or when deep adrenal vein cannulation cannot be confirmed radiologically.

Adenoma↗
PubMed1981

Thyroid hormone levels after acute L-thyroxine loading in hypothyroidism.

While extrathyroidal conversion of T4 to T3 sustains circulating T3 blood levels in patients receiving maintenance doses of L-T4, the serum T3 rise after the acute administration of large doses of L-T4 may involve an additional mechanism, T3 contamination in L-T4 preparations. L-T4 (1000 micrograms; Synthroid) was given orally to four noncompliant hypothyroid individuals (mean T4, 1.0 micrograms/dl; mean T3, 28 ng/dl). Continuously withdrawn blood sampling revealed a mean rise in serum T4 to 7.7 micrograms/dl at 4 h and a parallel rapid mean rise in serum T3 to 66 ng/dl (136% over baseline) at 4 h. RIA analysis of the experimental batches of Synthroid revealed 0.7-0.9% T3 contamination. Oral administration of 5 or 10 micrograms Cytomel (T3; corresponding to 0.5% and 1% T3 contamination in 1000 micrograms Synthroid) to two of the hypothyroid subjects at a later date resulted in T3 serum elevations 12% and 68% as great as post 1000 micrograms L-T4. To eliminate basal hormone changes between these experiments, a third subject received 7.5 micrograms Cytomel on day 1 (corresponding to the measured T3 contamination in 1000 micrograms Synthroid), followed by 1000 micrograms Synthroid on day 2. Resulting peak T3 levels were identical. In summary, hypothyroid individuals rapidly absorb acute L-T4 loads, with parallel increases in T4 and T3 blood levels. The major source of this T3 elevation is the contaminant in L-T4 preparations. This degree of T3 contamination becomes clinically significant in acute large dose T4 regimens and results in euthyroid levels of T3.

Fasting↗
PubMed1981

The effect of prostaglandin inhibition on renin release. A comparison of furosemide and low-sodium stimulation tests.

Furosemide administration is considered comparable to sodium restriction and upright posture as a stimulation test of PRA. This view can be questioned if different mechanisms of renin release are involved. Prostaglandins appear to be an important mediator of renin release. Using a prostaglandin antagonist, indomethacin, we attempted to assess the relative role of prostaglandins in the two renin stimulation tests. Eleven healthy volunteers on a high-sodium intake had PRA and PA measured in response to furosemide stimulation before and during indomethacin administration and then in response to sodium restriction combined with upright posture before and during indomethacin. Supine PRA was 0.41 ng/ml/hr on high sodium and 0.19 after indomethacin (p less than 0.05). On low sodium, the supine PRA was 2.07 ng/ml/hr and 0.98 after indomethacin (p less than 0.05). The increase in PRA (delta PRA) was 3.26 ng/ml/hr with furosemide stimulation and 1.23 after indomethacin (p less than 0.025). The PRA was 3.71 ng/ml/hr with low-sodium stimulation and upright posture and 2.53 after indomethacin (NS). PA paralleled PRA except that there was no suppression of supine values with indomethacin. We conclude that prostaglandins mediate baseline renin secretion and renin stimulation in response to furosemide. However, no comparable prostaglandin mediation could be demonstrated during renin stimulation secondary to sodium restriction. The two standard renin stimulation tests appear to involve different mechanisms of renin release.

Adult↗
PubMed1980

Integrated concentration of epinephrine and norepinephrine in normal subjects and in patients with mild essential hypertension.

Since the level of plasma catecholamines fluctuates rapidly during the day, measurement in a single blood sample could be misleading. A portable nonthrombogenic blood withdrawal system, permitting normal activity and sleep, was used for obtaining the 24-h integrated concentration (IC) of epinephrine (E) and norepinephrine (NE) in 46 normal control subjects, 30 patients with mild essential hypertension, and 1 patient with pheochromocytoma. The mean IC of E (ICE) and the mean IC of NE (ICNE) of the control subjects were 31 +/- 15 and 194 +/- 106 pg/ml, respectively (mean +/- 1 SD). The mean ICE and ICNE of the essential hypertensive patients were 30 +/- 21 and 224 +/- 90 pg/ml, respectively. No significant difference could be found between the levels found in essential hypertensive and normal control subjects. The levels of ICE and ICNE in the patient with pheochromocytoma were 1350 and 882 pg/ml, respectively, which are 88 and 6.5 SD above the mean of the normal control subjects.

Adolescent↗
PubMed1980

A comparative study of urinary 17-hydroxycorticosteroids, urinary free cortisol, and the integrated concentration of plasma cortisol.

The discriminatory power of three clinical tests for adrenal activity are compared by measuring the variability of the results obtained in 40 normal control subjects, 35 patients with mild essential hypertension, and 13 patients with Cushing syndrome. The variance of the 24-h integrated plasma concentration of cortisol was significantly (P < 0.0001) smaller than the variance of the 24-h urinary excretion of 17-hydroxycorticosteroids and free cortisol. While the 24-h urinary excretion of 17-hydroxycorticosteroids and free cortisol of the patients with Cushing syndrome overlapped with the corresponding values of the normal and hypertensive subjects, their integrated cortisol concentration did not exhibit any overlap.

17-Hydroxycorticosteroids↗
PubMed1979

Effect of adrenal suppression with dexamethasone in essential hypertension.

The 24-h integrated plasma concentration of aldosterone (IC-ALDO), PRA (IC-PRA), and cortisol (IC-F) were measured in 34 male patients with uncomplicated mild essential hypertension and 15 matched normal controls using a portable 24-h continuous nonthrombogenic blood withdrawal system. The hypertensive were subsequently given 0.5 mg dexamethasone three times per day, resulting in suppression of their urinary excretion of 17-hydroxycorticosteroids and free cortisol. The diastolic blood pressure of the hypertensives fell during adrenal suppression from 104 +/- 5 to 96 +/- 8 mm Hg (mean +/- 1 SD; P less than 0.0001). The systolic pressure fell from 150 +/- 16 to 148 +/- 17 (P greater than 0.01). Baseline values for IC-F, IC-ALDO, and IC-PRA were similar in hypertensive subjects and normal controls. After treatment with dexamethasone for 8 weeks, IC-F in the hypertensives decreased from 7.8 +/- 2.1 to 0.7 +/- 0.6 microgram/dl (P less than 0.0001). There was no associated change in IC-ALDO or IC-PRA. Thus, the fall in diastolic blood pressure in response to dexamethasone was associated with suppression of IC-F, without demonstrable changes in other endocrine or biochemical factors measured.

Adrenal Glands↗
PubMed1978

The integrated concentration of plasma renin activity and aldosterone in essential hypertension.

Measurement of the integrated concentration is most suited for the study of blood components that fluctuate rapidly. The integrated concentration of plasma aldosterone (IC-ALDO) and plasma renin activity (IC-PRA) were measured in 24 patients with essential hypertension and in 10 normal adult subjects, using a non-thrombogenic 24-hour constant blood withdrawal system. The integrated concentration of plasma aldosterone in the control subjects was 7.7 +/- 1.8 ng/100 ml (mean +/- 1 SD). Eight hypertensive patients had IC-ALDOs that were more than 3 standard deviations above the mean. Although the mean IC-PRA of the hypertensive patients was lower than the mean of controls (0.6 +/- 0.6 and 0.9 +/- 0.6, respectively), the difference was not significant. However, high integrated concentration of plasma aldosterone was mostly associated with low integrated concentration of plasma renin activity. Consequently, the ratio of IC-ALDO to IC-PRA in the hypertensive patients was significantly higher (p less than 0.001). In six hypertensive patients the ratio was more than 4 standard deviations above the mean for the normal control subjects (12.2 +/- 7.6). Individuals with inappropriately high integrated concentrations of plasma aldosterone can therefore be identified by the simultaneous determination of IC-ALDO and IC-PRA.

Adult↗
PubMed1977

Attempted treatment of inoperable pheochromocytoma with streptozocin.

Currently the only treatment available for inoperable pheochromocytoma is symptomatic and palliative with alpha- and beta- adrenergic blockade. Pheochromocytoma is a tumor of chromaffin tissue derived from the neural crest and closely related to other APUD (amine precursor uptake and decarboxylation) cell tumors, including those of the pancreatic islets. Streptozocin has been used with varying success in some of these tumors and therefore merited a trial in pheochromocytoma. We used streptozocin to treat two patients with inoperable pheochromocytoma; the drug failed to have any effect, either on catecholamine excretion or tumor growth.

Adult↗
PubMed1975

Symptomatic Rathke's cleft cyst with amyloid stroma.

A patient with panhypopituitarism and visual field defects due to a Rathke's cleft cyst is presented. These cysts are commonly found in random pituitaries examined at necropsy, but rarely produce symptoms. Subtle endocrine deficiencies, however, may now be uncovered more frequently with modern diagnostic techniques. An unusual and unreported feature of this cyst was an apudamyloid stroma. This would imply that cells derived from the neural crest participate in the formation of the cyst. Recognition of these cysts at the time of operation is important in avoiding confusion with pituitary adenomas and unnecessarily aggressive treatment.

Adenoma↗
PubMedDate not supplied

Red cell cotransport activity and sodium content in black men. Relationship to essential hypertension.

Furosemide-sensitive sodium and potassium cotransport and intracellular sodium content ([Na]i) were measured in erythrocytes (red blood cells, RBCs) from a population of 90 adult black men with and without essential hypertension (EH). The mean values for sodium cotransport activity, expressed as furosemide-sensitive Na efflux (mmol/liter RBC/hr), were not significantly different among the EH patients and two control groups, normotensive subjects with a positive history (N+) and those with a negative family history (N-) for hypertensive disease (EH: 154 +/- 123, n = 53; N+: 167 +/- 93, n = 12; and N-: 207 +/- 142, n = 20; all values are means +/- SD). The mean [Na]i 9.66 +/- 3.02 mmol/liter RBC (n = 56) for the EH group was greater than the mean value for the N- control group (7.96 +/- 1.97, n = 20; p less than 0.05). The N+ group also displayed a higher mean [Na]i (10.38 +/- 3.18, n = 12; N+ vs N- p less than 0.01). Although there was substantial overlapping of [Na]i values between the groups and no clear dividing line, the distribution curve of the [Na]i values in EH was skewed toward higher concentrations than in N-. Nevertheless, we must conclude that erythrocyte cotransport and [Na]i are not clinically useful in the identification of EH in black men.

Adult↗