Unusual results from immunoassays and the role of the clinical endocrinologist.
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Animals↗
Biomedical subjects
John W Honour
Publications and source records attributed to John W Honour.
High-performance liquid chromatography for hormone assay.
High-performance liquid chromatography (HPLC) is a refinement of traditional column chromatographic techniques. The speed of analysis and the resolution are increased with new column-packing materials and eluant pumped through the column at high pressure. The potential for achieving measurements of hormones in small volumes of plasma or urine is limited, both in normal and pathological situations. Using HPLC with ultraviolet absorption, the detection limit is only nanogram amounts of hormones per milliliter of blood serum. The applications of the technique to specific hormones from recent and older literature will be used throughout this chapter to illustrate aspects of the technology.
Adrenal Cortex Hormones↗
Gas chromatography-mass spectrometry.
Gas chromatography-mass spectrometry (GC-MS) has been used in hormone assays particularly for steroids in biological fluids. The combination of GC with MS exploits the high-resolving power of gas chromatography to separate closely related molecules, and the ability of the MS to provide precise data for identification and quantification of the separated substances. GC-MS is a very powerful technique for analysis with specificity of hormones in biological fluids. The general principles of GC-MS are described in this chapter along with some examples that illustrate specific applications of hormone analysis.
Adrenal Cortex Hormones↗
Short-term phytoestrogen supplementation alters insulin-like growth factor profile but not lipid or antioxidant status.
Phytoestrogens are plant compounds that have been proposed to have a variety of health benefits. The aim of this study was to assess the effects of these compounds on a number of physiological endpoints. Subjects were given a single intake of a phytoestrogen-rich (80 mg total phytoestrogens) supplement containing soy, rye and linseed (Phase 1), followed by a week-long intervention using the same supplement (Phase 2) (80 mg total phytoestrogens daily). A number of biochemical endpoints were assessed including urinary phytoestrogen metabolites, lipids, antioxidant status, DNA damage and insulin-like growth factor-1 (IGF-1) and IGF binding protein-1 (IGFBP-1) and -3 (IGFBP-3). Ten healthy female subjects took part in the study. Excretion of the isoflavones genistein, daidzein and equol in urine increased in both phases of the study. No other endpoint was altered in Phase 1. However, in Phase 2, concentrations of IGF-1 and IGFBP-3 were increased by phytoestrogen supplementation [IGF-1, median (IQ range), baseline 155 (123, 258), postweek 265 (228, 360) ng/ml, P<.05; IGFBP-3, baseline 3725 (3631, 4196), postweek 4420 (4192, 4935) ng/ml, P<.05]. There was no effect of supplementation on lipids or markers of antioxidant status. Short-term phytoestrogen supplementation increases urinary phytoestrogen excretion and increases IGF-1 and IGFBP-3. These results require elucidation in further controlled studies.
Adult↗
The fight for fair play.
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Doping in Sports↗
Opposing influences of prenatal and postnatal weight gain on adrenarche in normal boys and girls.
Associations between low birth weight and higher adrenal androgen secretion before puberty have yet only been reported in case-control studies in girls. We examined the influence of birth weight and early postnatal weight gain on overnight-fasting adrenal androgen and cortisol levels in 770 children from a large normal United Kingdom birth cohort at age 8 yr. In univariate analyses, adrenal androgen levels were inversely related to birth weight sd score in each sex [dehydroepiandrosterone sulfate in boys: regression coefficient (B) = -2.5 microg/dl/SD; 95% confidence interval (CI), -4.7 to -0.2; in girls: B = -3.8 microg/dl/SD; 95% CI, -6.2 to -1.4; androstenedione in boys: B = -0.15 nmol/liter/sd, 95% CI, -0.25 to -0.6; in girls: B = -0.13 nmol/liter/SD; 95% CI, -0.24 to -0.02). In multivariate analyses, both lower birth weight and larger current body weight predicted higher adrenal androgen levels (P < 0.005 for all comparisons). Allowing for current weight, children who showed rapid postnatal weight gain between 0 and 3 yr had higher dehydroepiandrosterone sulfate (P = 0.002) and androstenedione (P = 0.004) levels at 8 yr. In contrast, cortisol levels were unrelated to birth weight or current body size. In summary, the relationship between lower birth weight and higher childhood adrenal androgen levels was continuous throughout the range of normal birth weights, and was similar in boys and girls. Adrenal androgen levels were highest in small infants who gained weight rapidly during early childhood. We suggest that higher adrenal androgen secretion could contribute to links between early growth and adult disease risks, possibly by enhancing insulin resistance and central fat deposition.
Adrenal Cortex↗
Altered cortisol metabolism in polycystic ovary syndrome: insulin enhances 5alpha-reduction but not the elevated adrenal steroid production rates.
Androgen excess in women with polycystic ovary syndrome (PCOS) may be ovarian and/or adrenal in origin, and one proposed contributing mechanism is altered cortisol metabolism. Increased peripheral metabolism of cortisol may occur by enhanced inactivation of cortisol by 5alpha-reductase (5alpha-R) or impaired reactivation of cortisol from cortisone by 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) resulting in decreased negative feedback suppression of ACTH secretion maintaining normal plasma cortisol concentrations at the expense of androgen excess. We have tested whether any enzyme dysregulation was related to circulating insulin or androgen concentrations in women with PCOS and have sought to clarify their relationship with obesity. First, to avoid obesity-related effects on cortisol metabolism, 18 lean women with PCOS were compared with 19 lean controls who were closely matched for body mass index (BMI). Second, the impact of obesity was studied in a cross-section of 42 PCOS women of a broad range of BMI. We measured 24-h urinary excretion of steroid metabolites by gas chromatography/mass spectrometry and fasting metabolic and hormone profiles. Urinary excretion of androgens [androsterone (P = 0.003), etiocholanolone (P = 0.02), and C19 steroid sulfates (P = 0.009)], cortisone metabolites [tetrahydrocortisone (THE) (P = 0.02), alpha-cortolone (P < 0.001), beta-cortol + beta-cortolone (P < 0.001), cortolones (P < 0.001), and E metabolites (P < 0.001)], and TCM (P = 0.002) were raised in lean PCOS subjects when compared with controls. A significantly higher 5alpha-tetrahydrocortisol (5alpha-THF)/5beta-THF ratio (P = 0.04) and a significantly lower alpha-THF + THF + alpha-cortol/THE + cortolones ratio (P = 0.01) were found in lean PCOS women compared with lean controls, indicating both enhanced 5alpha-R and reduced 11beta-HSD1 activities. A decreased THE/cortolones ratio (P = 0.03) was also found in lean PCOS women compared with lean controls, indicating increased 20 alpha/beta-HSD activity. In the group of 42 PCOS subjects, measures of 5alpha/5beta reduction were positively correlated with the homeostasis model insulin resistance index (HOMA-R): alpha-THF/THF and HOMA-R (r = 0.34; P = 0.03), androsterone/etiocholanolone and HOMA-R (r = 0.32; P = 0.04), and total 5alpha /total 5beta and HOMA-R (r = 0.37; P = 0.02). A positive correlation was also found between measures of 5alpha-R and BMI (r = 0.37; P = 0.02). No correlation was found between measures of 11beta-HSD1 activity and indices of insulin sensitivity or BMI. We have demonstrated that there is an increased production rate of cortisol and androgens as measured in vivo in lean PCOS women. Insulin seems to enhance 5alpha reduction of steroids in PCOS but was not associated with the elevated cortisol production rate. The changes in 5alpha-R, 11beta-HSD1, and 20alpha/beta-HSD enzyme activities observed in PCOS may contribute to the increased production rates of cortisol and androgens, supporting the concept of a widespread dysregulation of steroid metabolism. This dysregulation does not seem to be the primary cause of PCOS because no correlation was found between serum androgen levels or urinary excretion of androgens with measurements of either 5alpha-R or 11beta-HSD1 activities.
11-beta-Hydroxysteroid Dehydrogenase Type 1↗
Benchtop mass spectrometry in clinical biochemistry.
Mass spectrometry has for many years enabled us to rapidly identify and quantify many different compounds in biological samples. The equipment is currently available in specialist centres investigating metabolic disorders and in toxicology laboratories. Improvements in sample introduction and refinements in the mass spectrometry hardware now allow higher sample throughput without extensive sample purification. Many mass spectrometers are compact and operated by computers that also assist data handling. Mass spectrometry has the potential to change hospital laboratory operations generally. Consideration of the practical and financial aspects of its application may reveal cost-effective means of improving the specificity of analyte assay. Considerable advantages are expected in the analysis of metabolites and drugs and in proteomics.
Biochemistry↗
Hypothalamic-pituitary-adrenal axis function after inhaled corticosteroids: unreliability of urinary free cortisol estimation.
Free cortisol in the urine (UFC) is frequently measured in clinical research to assess whether inhaled corticosteroids (ICS) cause suppression of the hypothalamic-pituitary-adrenal axis. Thirteen healthy male subjects received single inhaled doses (of molar equivalence) of fluticasone propionate (FP), triamcinolone acetonide (TAA), budesonide (BUD), and placebo in this single blind, randomized, cross-over study. UFC output was measured using four commercial immunoassays in samples collected in 12-h aliquots over 24 h. The cortisol production rate was assessed from the outputs of cortisol metabolites. UFC showed a 100% increase over placebo levels in the Abbott TDX assay after the administration of BUD. The other assays detected variable suppression (ranging from 29-61% suppression for FP, 30-62% suppression for TAA, and 25% suppression to 100% stimulation for BUD). Suppression was more pronounced in the first 12 h after TAA and in the second 12 h after FP. Similar suppression was found in each 12-h period after BUD. UFC estimation based on immunoassays after ICS may be an unreliable surrogate marker of adrenal suppression. Many of the published studies describing or comparing the safety of different ICS should be reevaluated, and some should be interpreted with caution.
Administration, Inhalation↗