Testosterone serum measurement

The goal of testosterone therapy in hypogonadal men is to mimic as closely as possible the normal serum concentration therefore, serum testosterone concentration must be monitored. With transdermal patches, the serum testosterone concentration fluctuates during the 24-hour period, with a peak value 6—9 hours after application and a nadir (about 50% of the peak) just before the next patch is applied (Figure 58-6). With testosterone gels, the mean serum testosterone concentration is relatively constant from one application to the next. Occasional random fluctuations can occur, so measurements should be repeated for any dose. When the enanthate or cypionate esters of testosterone are administered once every 2 weeks (typically in a dose of200 mg), the serum testosterone concentration measured midway between doses should be normal if not, the dose should be adjusted accordingly. 

Measure serum testosterone levels 14 days after initiation of therapy to ensure proper dosing. If the serum testosterone concentration is below the normal range, or if the desired clinical response is not achieved, the dose may be increased from 5 to 7.5 g AndroGel) or 10 g Testim) and from 7.5 to 10 g AndroGel), as instructed by the physician. 

E. Therapeutic response In anovulatory women, the goal of therapy is adequate follicular development as determined by ultrasound in combination with measurement of serum estradiol levels. In men, the aim of treatment is maintenance of serum testosterone levels within the normal range. 

Thienpont LM, Van Uytfanghe K, Blincko S, Ramsay CS, Xie H, Doss RC et al (2008) State-of-the-art of serum testosterone measurement by isotope dilution-liquid chromatography-tandem mass spectrometry. Clin Chem 54 1290-1297... 

Tai SS-C, Xu B, Welch MJ, Phinney KW (2007) Development and evaluation of a candidate reference measurement procedure for the determination of testosterone in human serum using isotope dilution liquid chromatography/tandem mass spectrometry. Anal Bioanal Chem 388 1087-1094... 

Given the above preclinical observations, patients in a clinical study were monitored closely during treatment (including measurement of testosterone, luteinizing hormone, follicle-stimulating hormone levels, alkaline phosphatase, and serum vitamin A concentrations). This phase I clinical study of TAG-101 was conducted to determine the safety, toxicity, and pharmacokinetics of this agent in patients with advanced cancer. Currently, the drug is in a phase I/II clinical trial for advanced hepatocellular carcinoma. 

Adrenal glands measurement of morning serum cortisol concentration or cosyntropin stimulation test Thyroid gland ultrasensitive determination of TSH Gonads sex hormone determinations (estradiol in women and testosterone in men) and gonadotropins... 

Pituitary reserve is almost never compromised in patients with small pituitary tumors, so testing is usually limited to patients with large tumors or specific clinical indications, (see Box 50-6, A). For most patients with large pituitary tumors, in addition to history and physical examination, an adequate evaluation of endocrine function before surgery can be performed based on laboratory measurements of serum PRL, TSH, LH, FSH, sex steroids (testosterone in males and estradiol in females), serum sodium, and results of a morning serum cortisol or ACTH stimulation test. 

Evaluation of Endocrine Parameters Serum testosterone should be measured especially when the patient history or physical examination suggests deficient development of secondary sex characteristics. Patients with borderhne or suppressed testosterone concentrations are... 

Either serum or heparinized plasma is used to measure total or free testosterone. Testosterone is subject to a diurnal variation, reaching a peak concentration between 0400 hours and 0800 hours. Therefore, morning specimens are preferred. Specimens are stable for a week (men) or 3 days (women) refrigerated and for up to 1 year frozen at 20 No steroids, thyroid, ACTH, estradiol, or gonadotropin medications should be given for 48 hours before sample collection. Most assays are standardized for serum or heparinized plasma. Other anticoagulants such as ethylene-diaminetetraacetic acid (EDTA) may give different values. In certain RIA assays, presence of EDTA appears to cause a 10% decrease in total testosterone concentrations. ... 

Only a small fraction (1% to 2%) of imconjugated testosterone exists fireely (non-protein bound) in serum or plasma. None of the conventional assay methods, including RIA, is sufficiently sensitive to quantify the free steroid directly in a protein-free ultrafiltrate of plasma. Instead, the free steroid is estimated in plasma by adding a known amount of radiolabeled compound to the sample and allowing labeled and unlabeled compounds to reach equilibrium in their competition for the same binding sites on the proteins. Bound and free radiolabeled fractions are then separated and the ratio of free labeled to total labeled compound is determined. At equilibrium, this ratio is taken as a measure of the free testosterone fraction. An estimate of serum free testosterone can then be calculated by multiplying the free testosterone fraction by the total testosterone concentration. 

Boots LR, Potter S, Potter D, Azziz R. Measurement of total serum testosterone levels using commercially available kits High degree of between-kit variability. Fertil Steril 1998 69 286-92. 

A. Wang C, Catlin DH, Demers LM, Starcevic B, Swerdloff RS. Measurement of total serum testosterone in adult men Comparison of current laboratory methods versus Liquid chi omatography-tandem mass spectrometry. J Clin Endocrinol Metab 2004 89 534-43. 

Wheeler MJ, Shaikh M, Jennings RD. An evaluation of 13 commercial kits for the measurement of testosterone in serum and plasma. Ann Clin Biochem 1986 23(Pt 3) 303-9. 

Serum concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone concentrations were measured in rats exposed for 13 weeks to PCB 28 or PCB 77 in food (Desaulniers et al. 1997). No changes, relative to the control group, were observed at doses of 500 pg/kg/day PCB 28 or 75 pg/kg/day PCB 77. Acute intraperitoneal administration of PCB 126 in adult rats caused decreased... 

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