Endocrine alterations in the aging male

Training-induced impairment of endothelial function in track and field female athletes

Professional athletes are often exposed to high training loads that may lead to overfatigue, overreaching and overtraining that might have a detrimental effects on vascular health. We determined the effects of high training stress on endothelial function assessed by the flow-mediated dilation (FMD) and markers of glycocalyx shedding. Vascular examination as well as broad biochemical, hormonal and cardiometabolic evaluation of sprint and middle-distance female runners were performed after 2 months of preparatory training period and compared to age-matched control group of women. Female athletes presented with significantly reduced FMD (p < 0.01) and higher basal serum concentrations of hyaluronan (HA) and syndecan-1 (SDC-1) (p < 0.05 and p < 0.001, respectively), that was accompanied by significantly lower basal serum testosterone (T) and free testosterone (fT) concentrations (p < 0.05) and higher cortisol (C) concentration (p < 0.05). It resulted in significantly lower T/C and fT/C ratios in athletes when compared to controls (p < 0.01). Moreover, fT/C ratio were significantly positively correlated to FMD and negatively to HA concentrations in all studied women. Accordingly, the training load was significantly negatively correlated with T/C, fT/C and FMD and positively with the concentrations of HA and SDC-1. We concluded that young female track and field athletes subjected to physical training developed impairment of endothelial function that was associated with anabolic-catabolic hormone balance disturbances. Given that training-induced impairment of endothelial function may have a detrimental effects on vascular health, endothelial status should be regularly monitored in the time-course of training process to minimalize vascular health-risk in athletes.

Lrriq1 is an essential factor for fertility by suppressing apoptosis

PURPOSE

Leucine-rich repeats and IQ motif containing 1 (LRRIQ1) gene is reportedly associated with plasma inhibin B levels. However, the function of LRRIQ1 remains unknown. In this study, we generated Lrriq1 knockout mice (Lrriq1-/- mice) and examined the effects of LRRIQ1 on inhibin B and fertility.

METHODS

Lrriq1-/- mice were generated using CRISPR/Cas9 genome editing technology. The expression of Inhibin B was examined by Western blotting using a protein extracted from the testis of a 3-month-old male mouse. Mating experiments were conducted using 7-week-old Lrriq1-/- mice and wild-type (WT) mice to examine fertility. Sperm concentration and sperm motility were measured using 3-month-old male mice.

RESULTS

Expression analysis of inhibin B revealed that Lrriq1-/- mice exhibited reduced mRNA and protein levels of inhibin alpha (Inha), which constitutes the α subunit. In the mating experiment, the litter size of Lrriq1-/- male mice was 4.3 ± 2.9, which was significantly lower than that of WT male mice (8.3 ± 1.3) (p < 0.001). No difference in sperm count was observed between Lrriq1-/- and WT male mice; however, sperm motility (%) was significantly reduced in Lrriq1-/- mice (48.4 ± 4.9) when compared with WT mice (70.2 ± 4.7) (p < 0.001). Based on TUNEL staining, the testes and epididymal sperm of Lrriq1-/- mice showed high numbers of apoptosis-positive cells.

CONCLUSION

Lrriq1 knockout reduced sperm motility and litter size by inducing apoptosis of testicular germ cells and epididymal sperm.

Insulin-like Growth Factor 1 and Prolactin Levels in Chimpanzees (Pan troglodytes) Across the Lifespan

As human and chimpanzee genomes show high homology for IGF1 and PRL, we analyzed the sera of 367 healthy chimpanzees obtained during routine physical examinations in a single colony and measured chimpanzee insulin-like growth factor (IGF)-1 and prolactin (PRL) levels across the lifespan using standard human immunoassays. Assuming chimpanzee IGF-1 levels peak during puberty as in humans, we randomly defined puberty as the age at which most IGF-1 levels were equal to or above the 90^th percentile for each sex (males, ages ≥7.00 but <9.20 years; females, ≥5.00 but <8.00 years). IGF-1 levels steadily increased at a similar rate in juvenile males and females and peaked in puberty, strongly correlating with age, then slowly decreased faster in adult males than in adult females. As a group, males had a higher mean IGF-1 level than did females, but comparison by age category showed similar mean IGF-1 levels in males and females. PRL levels increased with age in females more than in males and levels were twice as high in females than in males. One pubertal male reported to have short stature had lower IGF-1 and weight compared with other males in the age group, confirming suspected growth hormone deficiency; a second male of normal height but low IGF-1 may have had delayed puberty. Overall, results show that differences in IGF-1 levels over the lifespan in this cohort of chimpanzees largely mimic those seen in humans, while patterns of PRL changes are less similar.

Immunohistomorphometric Changes of The Pituitary Gonadotropic Cells After Testosterone Application in a Rat Model of the Andropause

Andropause, the culminating phase of male ageing, is characterized by deregulation of the hypothalamic-pituitarygonadal axis and low circulating free testosterone. The aim of this study was to investigate the immunohistomorphometric characteristics of the pituitary gonadotropic i.e. follicle-stimulating hormone (FSH) and the luteinizing hormone (LH) producing cells after testosterone application in a rat model of the andropause. Middle-aged Wistar rats were divided into orchidectomized (ORX; n=8) and testosterone treated orchidectomized (ORX+T; n=8) groups. Testosterone propionate (5 mg/kg b.m./day) was administered for three weeks, while the ORX group received the vehicle alone. Immunohistochemically stained FSH and LH cells underwent morphometric and optical density-related analysis, while circulating concentrations of the sex steroids were measured by immunoassays. Serum concentrations of testosterone and estradiol were significantly (p<0.05) increased by 24 and 2.7 fold respectively, compared to the ORX group. The volume of FSH and LH cells was significantly (p<0.05) decreased by 51.3% and 56.6% respectively, in comparison with ORX rats. Relative volume density of FSH and LH cells was also significantly (p<0.05) decreased by 54.0% and 72.8% respectively, compared to the ORX group. Results related to the optical density of gonadotropic cells (reflecting their hormonal content) were in line with the morphometric findings i.e. this parameter of FSH and LH cells was significantly (p<0.05) decreased by 25.7% and 16.2% respectively, in comparison with ORX rats. Conclusion: In conclusion, applied testosterone increased the serum concentrations of sex steroids, as well as it decreased morphometric parameters and optical density of gonadotropic cells in ORX rats.

Iodine nutrition and thyroid diseases in Chengdu, China: an epidemiological study

OBJECTIVE

To assess the iodine nutritional status and investigate the prevalence of thyroid diseases in a community population in Chengdu, China.

METHODS

Eighty school-age children were randomly selected for measurements of urinary iodine concentration. A total of 1500 residents over the age of 18 who had lived in Chengdu for more than 5 years were selected by stratified cluster sampling. Serum thyroid hormone concentrations and thyroid autoantibodies were measured, and thyroid ultrasonography was performed.

RESULTS

The median urine iodine concentration was 184 µg/l in school-age children. The prevalence of clinical hyperthyroidism, subclinical hyperthyroidism, clinical hypothyroidism and subclinical hypothyroidism was 0.97%, 1.95%, 0.90% and 5.55%, respectively. The prevalence of thyroid autoantibodies and thyroid nodules was 15.82% and 16.87%, respectively. The prevalence of clinical hyper- and hypothyroidism was greater in females than in males (P < 0.05). The prevalence of subclinical hyper- and hypothyroidism, thyroid nodules and thyroid autoantibodies increased significantly with age (P < 0.05). The rate of new abnormal TSH was 9.37%, and the average serum Thyroid Stimulating Hormone (TSH) concentrations increased with age. When TSH >0.71 mU/l, the prevalence of positive TPOAb and/or TgAb increased significantly with rising concentrations of TSH (P < 0.05); however, the prevalence of thyroid nodules did not increase with escalating concentrations of TSH (P = 0.09).

CONCLUSION

Subclinical thyroid diseases, especially subclinical hypothyroidism and thyroid nodules, are common in an iodine sufficient area. Females and the elderly might benefit from routine screening for thyroid diseases, followed by appropriate detection and treatment.

Life events are positively associated with luteinizing hormone in middle age adult men: role of cortisol as a third variable

Previous studies have tested the relationship between chronic stress and sex hormones, but inconsistent results have been found. One possibility is that this association may depend on other biological factors. This study examined the relationship between stressful life events (LE) and sex hormones in men, and whether cortisol is involved in this relationship. From a total number of 2906 men who completed a screening for the early detection of prostate cancer, 139 healthy men (mean ± SD age, 57.8 ± 5.7 years) were included in this study. Participants were assessed with the Holmes and Rahe questionnaire in relation to their experience of LE during the previous 1-5 years. Salivary and serum cortisol was measured at 08:00-09:00 h, as well as luteinizing hormone (LH), total testosterone, epinephrine (E) and norepinephrine (NE). LE weight sum and LE number positively correlated with LH (r = 0.293, p = 0.004; r = 0.220, p = 0.031, respectively). In a multiple regression analysis, LE-sum explained an additional and significant 10.4% of the variance in LH levels, after statistically controlling for the effects of age, waist circumference (WC) and BMI (F(1,90) = 6.61, p < 0.05). Importantly, cortisol interacted with LE in relation to total testosterone. In men with high cortisol values (≥15.4 µg/dl), there was a statistically significant positive relationship between LE number and total testosterone levels (p = 0.05), while LE were unrelated to total testosterone in men with low cortisol. LE correlated with sex hormones, predicting LH values, and in men with high cortisol levels shows a possible moderator effect of cortisol on the relationship between LE and total testosterone.

Prolonged high iodine intake is associated with inhibition of type 2 deiodinase activity in pituitary and elevation of serum thyrotropin levels

Our previous epidemiological study indicated that excessive intake of iodine could potentially lead to hypothyroidism. In the present study, we aimed to investigate the time and dose effect of iodine intake on serum thyrotropin (thyroid-stimulating hormone, TSH) levels and to explore the non-autoimmune regulation of serum TSH by pituitary type 2 deiodinase (D2). A total of 360 Wistar rats were randomly divided into five groups depending on administered iodine dosages (folds of physiological dose): normal iodine (NI), 3-fold iodine (3HI), 6-fold iodine (6HI), 10-fold iodine (10HI) and 50-fold iodine (50HI). At 4, 8, 12 and 24 weeks after administration of sodium iodide, blood was collected for serum TSH measurement by chemiluminescent immunoassay. Pituitaries were also excised for measurement of TSHβ subunit expression, D2 expression and activity, monocarboxylate transporter 8 (MCT8) and thyroid hormone receptor β2 isoform (TRβ2) levels. The results showed that iodine intake of 10HI and 50HI significantly increased pituitary and serum TSH levels from 8 to 24 weeks (P < 0·05 v. NI). Excess iodine had no effect on D2 mRNA or protein expression; however, 10HI and 50HI administration significantly inhibited pituitary D2 activities from 8 to 24 weeks (P < 0·05 v. NI). Iodine had no effect on MCT8 or TRβ2 protein levels. We conclude that prolonged high iodine intake inhibits pituitary D2 activity and induces elevation of serum TSH levels. These findings may provide a potential mechanism of iodine excess-induced overt and subclinical hypothyroidism.

Reference limits for serum thyrotropin in a Japanese population

The aim of the present study was to establish new reference intervals for serum thyrotropin (TSH) levels in Japanese subjects without antithyroid antibodies. We reviewed the serum TSH level of all patients 20 years of age and over who attended the outpatient clinic of our hospital between January 1, 2003, and September 20, 2010. The thyroid gland of every patient was examined by ultrasonography, and subjects found to have a normal thyroid were chosen. The following subjects were excluded: subjects with past history of thyroid diseases; subjects whose serum was positive for antithyroid antibodies; pregnant women; patients taking medication that might affect their free thyroxine (fT(4)) level or TSH levels. Ultimately, 1388 subjects were included in the reference population. The serum TSH levels shifted to higher ranges as the age of the groups increased. The calculated reference range was 0.39-4.29 mIU/L in the 20-29-year-old group, 0.34-3.90 mIU/L in the 30-39-year-old group, 0.56-5.02 mIU/L in the 40-49-year-old group, 0.51-5.30 mIU/L in the 50-59-year-old group, 0.60-4.85 mIU/L in the 60-69-year-old group, 0.62-6.15 mIU/L in the over 70-year-old group. The results of this study showed that the upper limit of the normal range of serum TSH levels increased with age in a Japanese population. Since the number of elderly reference subjects was relatively small, further study is needed. Setting the age- and race-specific reference limits for serum TSH levels is important in order to prevent significant misclassifications of patients with abnormal TSH levels.

Obesity and age affect male fertility potential

A case-cohort study of 2,157 patients, aged 17-67 years was performed to assess the impact of body mass index and age on male fertility. Using a multiple regression analysis across the total cohort, only age correlated significantly with all spermiogram parameters and serum hormones, but in patients aged 20-30 years (n = 617) the total sperm count was significantly negatively correlated with body mass index.

Free testosterone and free dihydrotestosterone throughout the life span of men

OBJECTIVE

The dihydrotestosterone/testosterone ratio seems to be an important factor in the expression of androgenic activity, especially in the prostate and pilosebaceous unit. Whereas the decline of testosterone in aging men is well known, controversial data can be found concerning the age dependence of dihydrotestosterone levels. Hormonal values from our database served for the construction of the life span curve of free dihydrotestosterone/free testosterone ratio.

METHODS

The results of testosterone, dihydrotestosterone and SHBG determination obtained by immunoassays from 13,152 male patients were used for the calculation of free steroid content and the construction of the age dependence curves.

RESULTS

After initial high free dihydrotestosterone: free testosterone ratio in infancy it decreases at the start of puberty and remains practically without change from approx. 20 years of age till senescence.

CONCLUSION

The course of free dihydrotestosterone/free testosterone ratio demonstrates the role of dihydrotestosterone for androgen functions especially in prepubertal age.

Adaptations to short-term muscle unloading in young and aged men

INTRODUCTION

The purpose of this investigation was to determine whether young (21.7 yr) and aged (68.5 yr) men experienced similar responses to 7 d of muscle unloading (N = 10 per group).

METHODS

Unilateral lower limb suspension (ULLS) was used to impose muscle unloading of the knee extensors. To compare the effects of unloading on aged and young men, a repeated-measures factorial ANOVA was used to assess those effects on isometric strength, as well as strength, total work, and average power during isokinetic contractions conducted at 0.53, 1.05, and 2.09 rad.s(-1).

RESULTS

Data showed that at slower speeds of movement, only a main effect of unloading was identified with young and aged men displaying similar and significant (P < 0.05) ULLS-induced decrements in strength, work, and power. The decrease in isometric strength correlated well with loss of electromyographic activity of contracting muscles (r = 0.79, P = 0.0002). At higher speeds of isokinetic contractions, not only was a main effect of age detected (young > aged), but it was also revealed that aged men, but not young men, experienced significant unloading-induced declines in muscle performance. Moreover, unloading resulted in a significant increase in plasma cortisol, a potent catabolic hormone, only among aged men. In contrast to other variables assessed, muscle endurance, quantified during 30 repetitions completed at 3.14 rad.s(-1), did not differ between age groups, nor was it altered by unloading.

CONCLUSION

These findings suggest that young and aged men respond differently to muscle unloading, but in assessing muscle performance, these differences are manifested only during faster contractile velocities.

Skeletal muscle and bone: effect of sex steroids and aging

Both estrogen and testosterone are present in males and females. Both hormones contribute to the well being of skeletal muscle and bone in men and women, and there is evidence that the loss of sex hormones is associated with the age-related decline in bone and skeletal muscle mass. Hormonal supplementation of older adults to restore estrogen and testosterone levels to those of young men and women is not without penalty.

Evaluation of neuroendocrine status in longevity

It is well known that physiological changes in the neuroendocrine system may be related to the process of aging. To assess neuroendocrine status in aging humans we studied a group of 155 women including 78 extremely old women (centenarians) aged 100-115 years, 21 early elderly women aged 64-67 years, 21 postmenopausal women aged 50-60 years and 35 younger women aged 20-50 years. Plasma NPY, leptin, glucose, insulin and lipid profiles were evaluated, and serum concentrations of pituitary, adrenal and thyroid hormones were measured. Our data revealed several differences in the neuroendocrine and metabolic status of centenarians, compared with other age groups, including the lowest serum concentrations of leptin, insulin and T3, and the highest values for prolactin. We failed to find any significant differences in TSH and cortisol levels. On the other hand, LH and FSH levels were comparable with those in the elderly and postmenopausal groups, but they were significantly higher than in younger subjects. GH concentrations in centenarians were lower than in younger women. NPY values were highest in the elderly group and lowest in young subjects. We conclude that the neuroendocrine status in centenarians is markedly different from that found in early elderly or young women.

Initial study on the effects of Prestige oil on human health

The big oil tanker Prestige wrecked at 130 miles from the coast of Galicia, on the Northwest of Spain, in November 19, 2002. During the accident over 40,000 tons of oil were spilled, and along the next weeks 22,000 more reached the shore in the way of three black tides. A great number of people participated in the cleaning tasks. The objective of this study was to initially evaluate the damage caused by Prestige oil in exposed individuals both from the cytogenetic and the endocrine points of view. Exposure level was determined by analysing volatile organic compounds in the environment and heavy metals in blood. Cytogenetic damage was determined by sister chromatid exchanges (SCE), and plasmatic prolactin and cortisol levels were used as biomarkers of endocrine toxicity. Finally we have determined the possible influence of GST genetic polymorphisms (GSTM1 and GSTT1 deletion polymorphisms, GSTP1 Ala105Val) on the evaluated effects. The exposed population was classified according to the performed cleaning tasks in three groups: volunteers that collaborated for 1 week (N=25), hired manual workers (N=20) and hired high-pressure cleaner workers (N=23). The control population consisted of 42 individuals. Exposure to Prestige oil caused cytogenetic damage in exposed individuals, being its effect influenced by age, sex, tobacco consumption and GSTM1 polymorphism. With regard to endocrine toxicity, our results showed that xenobiotics present in Prestige oil induced alterations in hormonal status, and thus it may be considered as an endocrine disruptor. Therefore, the selected parameters have shown to be good indicators of toxicity related to exposure to Prestige oil. In addition, data obtained point to the importance of using protective devices in preventing the effects related to the exposure.

Adrenal steroids in adrenomyeloneuropathy. Dehydroepiandrosterone sulfate, androstenedione and 17alpha-hydroxyprogesterone

Adrenoleukodystrophy (ALD) and its adult variant adrenomyeloneuropathy (AMN) are X-linked diseases associated with a deficiency in the peroxisomal degradation of saturated very long chain fatty acids (VLCFA) resulting in an accumulation of VLCFA in the central and peripheral myelin, the adrenal cortex and the testis. Adrenal insufficiency with clinical hypocortisolism occurs in approximately two thirds of the patients with AMN. We studied the circulating adrenal hormones 17alpha-hydroxyprogesterone (17alpha-OHP), androstenedione and dehydroepiandrosterone sulphate (DHEAS) in 63 male AMN patients (age 17-65 years) and the DHEAS serum levels in 95 healthy male controls (age 30-65 years). 34 of the patients presented with the phenotype of only spinal cord and peripheral nerve disability without hypocortisolism, 29 of the patients presented with the phenotype of either additional hypocortisolism or Addison's syndrome only. Normal 17alpha-OHP concentrations were found in all patients with no significant difference between patients without and with hypocortisolism (6.07 +/- 0.61 nmol/l and 4.76 +/- 0.37 nmol/l). Androstenedione concentration was significantly (p < 0.01) lower in patients with hypocortisolism (2.99 +/- 0.65 pmol/l versus 5.71 +/- 0.68 pmol/l). As serum levels of DHEAS are agedependent we divided the two groups into two subgroups each (subgroup one: age 17-40 years, subgroup two: age 41-65 years). The DHEAS concentration of patients without and with hypocortisolism was significantly (p < 0.01) lower in both subgroups (1. 4.35 +/- 0.84 micromol/l, n = 15, 2. 15 +/- 0.28 micromol/l, n = 19; 1. 1.90 +/- 0.57 micromol/, n = 21, 2. 0.96 +/- 0.29 micromol/l, n = 8) compared to controls (1. 9.0 +/- 0.96 micromol/l; 2. 5.21 +/- 0.25 micromol/l). In conclusion, androstenedione and DHEAS serum concentrations are subnormal in all AMN patients and may therefore serve as sensitive markers of the adrenal function in adrenomyeloneuropathy.

Do differences in age specific androgenic steroid hormone levels account for differing prostate cancer rates between Arabs and Caucasians?

OBJECTIVE

Factors responsible for the low incidence of clinical prostate cancer in the Arab population remain unclear, but may be related to differences in androgenic steroid hormone metabolism between Arabs and other populations, especially as prostate cancer is believed to be androgen dependent. We therefore measured the levels of serum androgenic steroids and their binding proteins in Arab men and compared results obtained with values reported for Caucasian populations to determine if any differences could at least partially account for differences in incidence of prostate cancer rates between the two populations.

METHODS

Venous blood samples were obtained from 327 unselected apparently healthy indigenous Arab men (Kuwaitis and Omanis) aged 15-79 years. Samples were also obtained from 30 Arab men with newly diagnosed prostate cancer. Serum levels of total testosterone (TT), sex hormone binding globulin (SHBG), derived free androgen index (FAI); adrenal C19 -steroids, dehydroepiandrosterone sulfate (DHEAS) and androstenedione (ADT) were determined by chemiluminescent immunoassay. Age specific reference intervals, mean and median for each analyte were determined. Frequency distribution pattern for each hormone was plotted. The reference range for hormones with normal distribution was mean +/- 2SD and 2.5-97.5% for those with non-normal distribution. The mean serum levels of the hormones in Arab men with prostate cancer were compared with values in healthy age-matched Arab men.

RESULTS

There was a significant decrease between the 21-29 years age group and the 70-79 years age group for TT (-38.77%), DHEAS (-70%), ADT (-36%) and FAI (-63.25%), and an increase for SHBG (+64%). The calculated reference ranges are TT (2.73-30.45 nmol/L), SHBG (6.45-65.67 nmol/L), FAI (14.51-180.34), DHEAS (0.9-11.0 micromol/L) and ADT (0.54-4.26 ng/mL). The mean TT, SHBG, DHEAS and ADT in Arab men were significantly lower than those reported for Caucasians especially in the 21-29 years age group. Arab men with newly diagnosed prostate cancer had higher serum TT (P < 0.7), ADT (P < 0.2), SHBG (P < 0.2) and lower DHEAS (P < 0.008) compared to aged matched controls.

CONCLUSIONS

Serum TT, SHBG, DHEAS and ADT levels are significantly lower in Arab men compared to those reported for Caucasian men, especially in early adulthood. Arab men with newly diagnosed prostate cancer have higher circulating androgens compared to healthy controls. We suggest that low circulating androgens and their adrenal precursors in Arab men when compared to Caucasians may partially account for the relatively lower risk for prostate cancer among Arab men.

Prostate Cancer Risk: The Significance of Differences in Age Related Changes in Serum Conjugated and Unconjugated Steroid Hormone Concentrations Between Arab and Caucasian Men

INTRODUCTION

Factors responsible for the low incidence of clinical prostate cancer (3-8/100,000 men/year) in the Arab population remain unclear, but may be related to changes in steroid hormone metabolism. We compared the levels of serum conjugated and unconjugated steroids between Arab and Caucasian populations, to determine if these can provide a rational explanation for differences in incidence of prostate cancer between the two populations.

PATIENTS/METHOD

Venous blood samples were obtained from 329 unselected apparently healthy indigenous Arab men (Kuwaitis and Omanis) aged 15-80 years. Samples were also obtained from similar Arab men with newly diagnosed prostate cancer or benign prostatic hyperplasia (BPH). The samples were taken between 8:00 am and 12:00 noon. Serum levels of total testosterone, (TT), sex hormone binding globulin (SHBG), free androgen index (FAI); adrenal C19-steroids, dehydroepiandrosterone sulphate (DHEAS) and androstenedione (ADT) were determined using Immulite kits (Diagnostic Systems Laboratories Inc, Webster Texas, USA). The results obtained in Arab men were compared with those reported for similarly aged Chinese, German and White USA men.

RESULTS

In all four ethnic groups, median TT and FAI declined with age, while SHBG increased with age. However, the mean TT and SHBG was significantly lower (p < 0.01) and the FAI significantly higher in Arab men (p < 0.01) compared to German men only in 21-30 years age group. In the other age groups the levels of TT and SHBG were higher in the Germans but the differences were not statistically significant. In all the racial groups serum levels of DHEAS and ADT reached a peak by about 20 years of life, and then declined progressively. The mean DHEAS in American Caucasians aged 20-29 years was 11.4 micromol/l compared to 6.22 micromol/l in the Arabs (p < 0.001). The mean DHEAS in USA Caucasians aged 70-79 years was 2.5 micromol/l compared to 1.8 micromol/l (p < 0.03) in the Arabs. There was no significant difference in mean serum levels of DHEAS between German and USA men. Similarly, there was no significant difference in the level of the hormones between Arab and Chinese men. Arab men with newly diagnosed prostate cancer had high serum TT, SHBG and DHEAS compared to those without the disease.

CONCLUSIONS

The mean TT and SHBG was significantly lower in Arab men compared to Caucasian men especially in early adulthood. Caucasians have significantly higher serum levels of the precursor androgens DHEAS and ADT especially in early adulthood compared to Arab men. These observations of low circulating androgens and their adrenal precursors in Arab men may partially account for the decreased risk for prostate cancer among Arab men.

Reference intervals for important serum sex steroid hormones, prostate-specific antigen, insulin-like growth factor-1 and IGF binding protein-3 concentration in a normal Kuwaiti adult male population

OBJECTIVES

The purpose of this study was to determine the age-specific reference ranges for some important male sex steroid hormones, prostate-specific antigen (PSA), insulin-like growth factor-1 (IGF-1), and IGF binding protein-3 (IGFBP-3), for the Kuwaiti population.

SUBJECTS AND METHODS

Blood samples were taken from 398 consenting, fasting, healthy Kuwaiti males aged 15-80 years between 8.00 a.m. and 12.00 noon. The serum concentrations of total testosterone (TT), dehydro-epiandrosterone sulfate (DHEAS), androstenedione (ADT), sex hormone binding globulin, luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin, PSA, IGF-1 and IGFBP-3 were determined. A distribution curve was plotted and age-specific reference levels were determined for each analyte. The reference interval for parameters with a normal distribution (Gaussian) was mean +/- 2 SD, while for the non-normal distribution (non-Gaussian), it was 2.5-97.5 percentile. The reference intervals for the analytes obtained from this study were compared with those suggested by the kit manufacturers and currently used by the Ministry of Health, Kuwait Laboratories (MOHKL).

RESULTS

Serum IGFBP-3 and ADT had normal distribution while other analytes had non-normal distribution. The reference intervals from this study, manufacturers kit and MOHKL were as follows: TT 3-31, 9-60, 8-35 nmol/l; DHEAS 0.9-11, 1.0-7.3, 2.2- 15.2 micromol/l; ADT 0.5-4.3, 0.8-2.8, 2.0-9.2 nmol/l; LH 1-11, 0.8-7.6, 0.4-5.7 mIU/l; FSH 0.5-11, 0.7-11.1, 1.1-13.5 mIU/l; prolactin 42-397, 53-360, 80-230 nmol/l; IGF-1 41-542, 78-956, 71-261 ng/ml; IGFBP-3 88- 2,090, 900-4,000, 900-4,000 ng/ml, and PSA 0-3.1, 0-4, 0-4 ng/ml, respectively.

CONCLUSION

These data indicate that for Kuwaitis lower reference ranges must be used for serum TT, DHEAS, ADT, IGFBP-3 and PSA. There is no need to change the currently used reference interval for FSH whereas higher values must be used for LH, prolactin, and IGF-1.

Basal growth hormone concentrations in blood and the risk for prostate cancer: a case-control study

OBJECTIVE

To assess the relationship between basal serum growth hormone (GH) levels and prostate cancer risk.

METHODS

We conducted a population-based case-control study; cases included 68 men, aged 45-85 years, diagnosed with incident, primary, histologically confirmed, and clinically apparent (stage B and higher) prostate cancer. Controls included 240 men, frequency matched on age and residential area. Age, race, BMI, waist circumference, history of enlarged prostate, education, and current smoking status, were all considered as possible confounders.

RESULTS

We found a statistically significant trend of decreasing prostate cancer risk across increasing GH quintiles, in both crude (OR: 0.31, 95% CI: 0.12-0.83, P for trend 0.01) and adjusted models (OR: 0.35, 95% CI: 0.12-1.05, P for trend 0.03), in the highest compared to the lowest quintile, respectively.

CONCLUSIONS

Lower basal levels of GH in serum are associated with increased prostate cancer risk. The inverse association may be explained by the negative feedback loop generated by IGF-1 produced by the tumor on GH secretion.

Reference intervals of serum thyroid function tests in a previously iodine-deficient area

AIM

We undertook the present study to establish reference data for serum thyroid function tests in a previously iodine-deficient area.

METHODS

Data from 4298 individuals, 20-79 years of age were available for the present analysis. Thyroid function (thyrotropin [TSH], free triiodothyronine [FT(3)], and free thyroxine [FT(4)]) and serum autoantibodies to thyroperoxidase (anti-TPOAb) were evaluated from blood samples. Thyroid structure and size were measured by ultrasound.

RESULTS

A reference population was selected comprising 1488 persons (825 men) by excluding subjects with known thyroid diseases, and with yet unknown thyroid disorders such as goitre, inhomogeneous thyroid pattern, nodules, hypoechogenicity and anti-TPOAb seropositivity. Reference intervals for serum TSH, FT(3), and FT(4) were 0.25-2.12 mIU/L, 3.8-7.0 pmol/L, and 8.3-18.9 pmol/L, respectively. Reference serum TSH levels were not comparable to the reference values that were recently established for the U.S. population and most reference values slightly differed from the reference values provided by the manufacturers.

CONCLUSIONS

The reference ranges of thyroid function tests in this formerly iodine-deficient region are distinct from the reference ranges that were established in areas with iodine sufficiency. Creating a reference population in the present setting should include thyroid ultrasound in order to exclude yet undiagnosed thyroid disorders.

Performance characteristics of the IMMULITE 2000 insulin-like growth factor binding protein-3 assay

BACKGROUND

Insulin-like growth factor binding protein-3 (IGFBP-3) is the chief binding protein for insulin-like growth factors 1 and 2 (IGF-1 and IGF-2). Serum concentrations of IGFBP-3 are regulated by growth hormone (GH) and IGF-1 levels. Serum IGFBP-3 measurements are useful for diagnostic evaluations of short stature in children and acromegaly.

METHODS

A IGFBP-3 assay for the IMMULITE 2000 analyzer was evaluated for limit of detection, linearity, intra- and interassay imprecision, comparison to another commercially available assay, interference studies, and an adult reference interval.

RESULTS

The limit of detection was 0.006 mg/l. The assay was linear from 0.01 to 15.1 mg/l. The total interassay imprecision was <6% for IGFBP-3 concentrations of 1.1 and 4.4 mg/l. Comparison with a Nichols RIA method showed comparable results. Deming regression analysis gave a slope of 1.02+/-0.02, an intercept of 0.24+/-0.07, and a Sy/x of 0.33 (r=0.98) over the range tested (0.4 to 10.3 mg/l). Interference was <10% for all levels of bilirubin, triglyceride, and hemoglobin tested. The nonparametric reference interval for adults 26 to 61 years was 2.9 to 6.5 ng/ml.

CONCLUSIONS

The IMMULITE 2000 IGFBP-3 assay shows acceptable performance and is suitable for routine clinical use.