Endocrine Abstracts

Oestrogen analysis presents a significant challenge due to the low concentrations of these hormones, especially in the case of oestradiol, the most potent oestrogen which plays a crucial role in fertility, bone health, and various endocrine disorders. Traditional methods of measuring oestrogens, immunoassays, are unreliable at low concentrations, and have high cross-reactivity, leading to inaccurate results and potential misdiagnosis. Mass spectrometry offers a more selective and sensitive alternative, with less cross-reactivity. However, even with MS, the quantification of oestradiol remains difficult due to its poor ionisation efficiency, necessitating the use of highly sensitive liquid chromatography tandem-mass spectrometers (LC-MS/MS) and large sample volumes, particularly when measuring in post-menopausal women, men, and children. In this study, we aimed to develop a method capable of quantifying very low concentrations of oestrogens. We collected 24-hour urine from 51 healthy females aged 22-73 years. To increase sensitivity beyond that typically achieved with LC-MS/MS, we optimised a gas chromatography-mass spectrometry (GC-MS) method for detection of 11 oestrogens, including oestradiol, oestrone, and their hydroxy and methoxy derivatives. Steroids were extracted from 2mL of 24hr-urine, deconjugated, and derivatised into methyloxime-trimethylsilyl ethers. The oestrogens were quantified relative to an internal standard and calibration series. Our method successfully quantified low concentrations of oestrogens in both pre- and postmenopausal women. The most predominant forms of oestrogens found in the urine were oestradiol 41.6µg/24hr (10.4-53.1) and 2-methoxy-oestrone 26.8µg/24hr (16.0-46.4), less predominant were oestrone 2.2µg/24hr (1.3-5.0) and oestriol 2.2µg/24hr (0.8-6.2), all others oestrogen concentrations ranged 0.1-17.7µg/24hr. This approach demonstrated the sensitivity required for clinical applications where measuring low oestrogen levels is essential, such as in studies evaluating the efficacy of treatments like tamoxifen that aim to reduce total oestrogen load.