Radioimmunoassay of progesterone in saliva: a simplified technique using 125I-radioligand

A novel high-throughput assay for the measurement of salivary progesterone by liquid chromatography tandem mass spectrometry

Background

Liquid chromatography tandem mass spectrometry (LC-MS/MS) enables specific and sensitive quantification of steroids with a high throughput. Saliva sampling is advantageous for multisample profiling over longer periods of time, as it is non-invasive, cheap, can be carried out at home and does not require the attendance of clinical personnel. We developed a rapid LC-MS/MS for the measurement of salivary progesterone, frequently assessed as ovulation marker in patients desiring fertility.

Methods

Samples (300 μL) were prepared by supported liquid extraction using dichloromethane and were reconstituted in 40% methanol. Chromatography was performed using a C8 column with a water/methanol gradient containing 0.1% formic acid and 2 mmol/L ammonium acetate. Quantification was performed with a Waters TQ-S mass spectrometer.

Results

Total run time was 5.5 min. The lower limit of quantification was 20 pmol/L (1.2 fmol on column). Inter- and intra-assay comparison showed coefficients of variation and bias between measured and nominal concentrations of less than 11%. Mean recovery was 91%. Interference with a large set of natural and synthetic steroids was excluded. The assay was successfully applied to measure progesterone variation during the menstrual cycle ( n = 9) and diurnal variations during luteal phase ( n = 7) in regularly cycling women.

Discussion

We present a novel LC-MS/MS assay for the determination of salivary progesterone with high-throughput potential. The applicability of the assay for progesterone profiling during the menstrual cycle is demonstrated.

Metabolism of progesterone and testosterone in human parotid and submandibular salivary glands in vitro

Twenty-three parotid and twelve submandibular human salivary glands were used for analyzing in vitro metabolism of progesterone (P) and/or testosterone (T), in order to find out their possible contribution to the concentrations of salivary P or T. Glands were excised from 21 women and 14 men because of a stone, tumor or sialoadenitis, and the healthy tissue was used for incubation. The tissues were homogenized and incubated with 5 to 7 nmol/l of [14C]P or [14C]T for 2 h, extracted with methylacetate and subjected to two dimensional thin-layer chromatography. The thin-layer plates were autoradiographed, and the radioactivity of the different metabolites were counted to assess the amounts of metabolites formed. No lipoidal or conjugated steroids were formed. All of the radioactivity was associated with the free fraction of steroids. Both P and T were metabolized significantly more actively in male submandibular gland compared to male parotid gland (P < 0.05-0.01). No significant differences were found between female and male parotid glands, nor between the parotid glands of hormonally medicated (oral contraceptives or postmenopausal estrogen treatment) and non-medicated women. The submandibular glands more actively metabolized the steroids studied than the parotids (P < 0.01). The main metabolites were 20 alpha-hydroxy-4-pregnen-3-one for P, and androstenedione for T. In conclusion, the present results bring further evidence that the P or T levels in saliva may not be identical with the unbound steroid fraction in circulation, but a part of the steroids are metabolized in salivary glands. However, due to the rapid passage of steroids from blood to saliva, the metabolism demonstrated probably does not form an important source of error in salivary P and T measurements.

Daily measurements of salivary progesterone reveal a high rate of anovulation in healthy students

Daily concentrations of salivary progesterone (P) were measured from 32 women during a complete menstrual cycle. Seventeen of the subjects were university students and 15 were patients of an infertility clinic (a severe male-factor was verified as the cause of infertility in all of them). Commercially available reagents for radio-immunoassay of serum P were modified for salivary measurements, to yield acceptable precision and sensitivity (40 pmol/l). Good correlation (r = 0.93) was found between salivary and serum P concentrations in samples collected simultaneously. The follicular phase levels of salivary P were below 100 pmol/l, and those at the luteal peak were 390 +/- 45 pmol/l (mean +/- SEM, n = 24). From the menstrual salivary P concentration curves we identified the first day of significant elevation above mean follicular levels (T2) and thereafter calculated the cumulative sum of daily P concentrations until 95% of the luteal phase secretion had accumulated (C95). The time needed to reach C95 (designated T95) and logC95 were plotted in coordinates and used as the basis of evaluation of normal menstrual P secretion. The observations were distributed in two groups, one with clearly identifiable T2 and a distinct luteal-phase P (ovulation had occurred) and one with no identifiable T2 and absent luteal-phase P peak (indicative of anovulation). Interestingly, 47% of the student population had an abnormally low menstrual P profile while all the other subjects displayed a clear luteal-phase peak of salivary P. These data provide more evidence for applicability of salivary P measurements for diagnosis of corpus luteam function and highlight the difficulty of selecting representative reference populations in studies on female reproductive endocrinology.

The prediction of ovulation and monitoring of the fertile period

Simple and reliable methods have been sought for both predicting and confirming ovulation. Application of these methods could include management of infertile couples to aid in conception and for increasing the reliability of natural family planning (NFP) as a method of birth control. With the advent of specific hormone assays, serial measurements of estrogens, progesterone (and metabolites), and luteinizing hormone have been the gold standard of monitoring ovarian function in women. However, newer and simpler methodologies have been described and are currently either in use or being tested. These include the measurement of basal body temperature (BBT), the evaluation of the volume, consistency and electro-conductivity of cervicovaginal fluid, salivary steroid content and cellular enzymatic activity, the use of enzyme-linked immunosorbent assays applied to solid-phase formats, and the investigation of new hormonal molecules as markers of reproductive state and function. These new technologies are described herein and their potential for monitoring ovarian function is discussed.

Progesterone and estradiol in saliva after in vitro fertilization and embryo transfer

The importance of the luteal function to ensure adequate implantation prompted us to assay salivary estradiol (SE2) and salivary progesterone (SP) concentration serially after embryo transfer by simple and rapid radioimmunoassays to allow a noninvasive easily repeatable approach. SE2, which has fallen 1 day after human chorionic gonadotropin injection, increased after reimplantation (day 3), plateaued during approximately 1 week, and returned to basal levels before menstruation in absence of conception or in chemical pregnancy, whereas it increased steadily in successful pregnancy. SP increased in all the cases, formed a plateau, and returned progressively to basal levels before menstruation, whereas in ongoing pregnancy there was a transitory decline in the midluteal phase followed by a rapid and continuous increase, with a significantly higher ratio day 13/day 10 in successful pregnancy.