Short-Term Effects of Growth Hormone on Lipolysis, Glucose and Amino Acid Metabolism Assessed in Serum and Microdialysate of Healthy Young Men.

OBJECTIVE: We investigated direct effects of a therapeutic growth hormone dose on lipolysis, glucose and amino acid metabolism. METHODS: This crossover microdialysis trial involved six healthy male volunteers receiving single subcutaneous injections of both growth hormone (0.035 mg/kg) and placebo (0.9% sodium chloride). The investigation comprised three test days with standard diet. The first day served for adaptation, the second and third one for determining study data during 9 night hours with or without growth hormone. Abdominal subcutaneous microdialysate and blood were continuously collected and forwarded to a separate room next door where hourly taken samples were centrifuged and frozen until analysed. RESULTS: Growth hormone achieved the peak serum level after 3 h followed by a plateau-like course for the next 6 h. Glycerol in microdialysate started to rise 2 h following growth hormone injection achieving significance compared to placebo after 9 h (P<0.05). Serum glycerol increased 4 h after growth hormone administration achieving significance after 6 h (P<0.05). Glucose and amino acid concentrations showed neither in microdialysate nor in serum significant differences between growth hormone and placebo. Serum values of insulin and C-peptide revealed no significant difference between growth hormone and placebo. SUMMARY AND CONCLUSION: As the result of a high single subcutaneous dose of GH, persistent lipolysis can be shown in continuously collected microdialysate and blood, but no indication for gluconeogenesis or protein anabolism.

Start low, go slowly - mental abnormalities in young prolactinoma patients under cabergoline therapy.

Background Prolactin-secreting pituitary adenomas in childhood and adolescence are rare. First-line therapy consists of dopamine agonists (DAs) like cabergoline. Experience in treating prolactinomas in paediatric and adolescent patients is limited. Methods This study was a retrospective analysis of clinical data, laboratory data, radiological findings and medical treatment of paediatric and adolescent patients with prolactinomas between 2009 and 2018. Results Our cohort of nine patients had a median age at diagnosis of 13 years (range 5-17). Main presenting symptoms were weight gain, disorders of the pituitary-gonadal axis and headache. Treatment with cabergoline resulted in a marked reduction in prolactin concentration in all nine patients. Tumour mass reduction was confirmed by magnetic resonance imaging (MRI) scan in seven patients. Noteworthy is that cabergoline therapy triggered frequent adverse effects in a total of eight patients - seven of whom suffered from mental disorders, five of whom had neurological symptoms and five of whom had gastrointestinal problems. The adverse effects occurred at a median dose of only 0.5 mg/week (range 0.25-2.0). Most symptoms were alleviated after the cabergoline dose was lowered. Therapy discontinuation was not necessary in any patient. Conclusions Cabergoline effectively lowers prolactin levels and may reduce tumour mass in paediatric and adolescent patients with prolactinomas. Potential adverse effects may include mental disorders and behavioural problems even at low cabergoline doses. Low starting doses and careful individual dose adjustments are required to enable therapy adherence.

Evaluating the four most important salivary sex steroids during male puberty: testosterone best characterizes pubertal development.

Background During pubertal development in healthy boys, increased levels of different sex steroids occur which are responsible for sexual maturation and physical changes. However, relationships between various sex hormones and pubertal development stages have not been sufficiently studied. Methods The investigation included 165 normal boys (mean age 12.7±2.8 years, mean body mass index [BMI] 19.6±4.2 kg/m2). Pubic hair (PH) stages were stratified by Tanner and testicular volume (TV) by means of the Prader orchidometer and assigned to the prepubertal, pubertal and postpubertal development phase. Four different sex steroids (testosterone [TE], dehydroepiandrosterone [DHEA]/dehydroepiandrosterone-sulfate [DHEAS], androstenedione (AE), 17-hydroxyprogesterone [17-OHP]) were measured in saliva by enzyme-linked immunosorbent assay (ELISA) and as serum total steroids by different assays (radioimmunoassay [RIA], chemiluminescence immunoassay [CLIA], electrochemiluminescence immunoassay [ECLIA]). Validation of saliva-based ELISA tests included data related to inter- and intra-assay coefficients of variation (CVs), recovery and linearity. Results Using Spearman rank correlation, salivary steroids significantly correlated (p<0.001) with pubertal development: TE (TV r=0.74 and PH stages r=0.72), DHEA (r=0.58 and 0.62), AE (r=0.38 and 0.45) and 17-OHP (r=0.42 and 0.43). Correlations between salivary and serum concentrations of steroids were also statistically significant (p<0.001). Binomial logistic regression analysis revealed significant correlations between salivary TE and pubertal maturation during the development phases of prepuberty-puberty and puberty-postpuberty. Inclusion of further salivary steroids did not improve analysis results. Conclusions Salivary TE permits a good non-invasive characterization of pubertal maturation stages. The consideration of further salivary sex steroids did not improve diagnostic accuracy.

Transfer of Topical Testosterone to Subcutaneous Microdialysate, Blood and Saliva in Healthy Young Men.

OBJECTIVE: We evaluated percutaneous penetration of topical testosterone and subsequent transfer to subcutaneous tissue, blood and saliva. METHODS: This microdialysis trial involved eight healthy male volunteers. Five participants received a single dose of 50 mg testosterone gel on the abdominal skin and three untreated participants served as controls. Two microdialysis probes were inserted percutaneously into the abdominal subcutaneous adipose tissue. On the skin above one probe, testosterone gel was applied (ipsilateral side). A second control probe was inserted on the contralateral side. For the determination of total and free testosterone, samples of subcutaneous microdialysate, serum, and saliva were collected over six hours, frozen, and analysed using ELISA procedures. RESULTS: Testosterone values in the ipsilateral microdialysate of treated subjects increased significantly within 6 h after gel application compared to controls. Salivary testosterone levels showed a rapid increase within 20 min after transdermal application followed by a plateau phase with tenfold increased testosterone levels. Microdialysate testosterone of the contralateral site started to rise moderately within the normal range 1 h after administration of testosterone gel whereas total and free testosterone serum concentrations increased within 2 h in each case followed by a plateau phase. SUMMARY AND CONCLUSION: Single topical administration of testosterone gel leads to a continuous increase of testosterone in the subcutaneous ipsilateral microdialysate. Rapid salivary testosterone increase happens after gel administration followed by tenfold increased testosterone plateau values. Despite continuous influx, testosterone concentrations in serum, saliva, and contralateral microdialysate show a plateau formation thus avoiding testosterone excess.

Diurnal variation of phenylalanine and tyrosine concentrations in adult patients with phenylketonuria: subcutaneous microdialysis is no adequate tool for the determination of amino acid concentrations.

BACKGROUND: Metabolic control and dietary management of patients with phenylketonuria (PKU) are based on single blood samples obtained at variable intervals. Sampling conditions are often not well-specified and intermittent variation of phenylalanine concentrations between two measurements remains unknown. We determined phenylalanine and tyrosine concentrations in blood over 24 hours. Additionally, the impact of food intake and physical exercise on phenylalanine and tyrosine concentrations was examined. Subcutaneous microdialysis was evaluated as a tool for monitoring phenylalanine and tyrosine concentrations in PKU patients. METHODS: Phenylalanine and tyrosine concentrations of eight adult patients with PKU were determined at 60 minute intervals in serum, dried blood and subcutaneous microdialysate and additionally every 30 minutes postprandially in subcutaneous microdialysate. During the study period of 24 hours individually tailored meals with defined phenylalanine and tyrosine contents were served at fixed times and 20 min bicycle-ergometry was performed. RESULTS: Serum phenylalanine concentrations showed only minor variations while tyrosine concentrations varied significantly more over the 24-hour period. Food intake within the patients' individual diet had no consistent effect on the mean phenylalanine concentration but the tyrosine concentration increased up to 300% individually. Mean phenylalanine concentration remained stable after short-term bicycle-exercise whereas mean tyrosine concentration declined significantly. Phenylalanine and tyrosine concentrations in dried blood were significantly lower than serum concentrations. No close correlation has been found between serum and microdialysis fluid for phenylalanine and tyrosine concentrations. CONCLUSIONS: Slight diurnal variation of phenylalanine concentrations in serum implicates that a single blood sample does reliably reflect the metabolic control in this group of adult patients. Phenylalanine concentrations determined by subcutaneous microdialysis do not correlate with the patients' phenylalanine concentrations in serum/blood.