Maxson, W. S., & Hargrove, J. T. (1985). Bioavailability of oral micronized progesterone. Fertility and Sterility, 44(5), 622-626. https://doi.org/10.1016/s0015-0282(16)48977-6
Maxson WS, Hargrove JT. Bioavailability of oral micronized progesterone. Fertil Steril. 1985;44(5):622-626. doi:10.1016/s0015-0282(16)48977-6
Maxson, Wayne S., and Joel T. Hargrove. "Bioavailability of oral micronized progesterone." Fertility and Sterility, vol. 44, no. 5, 1985, pp. 622-626.
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Oral micronized progesterone reached mid-luteal levels in 10 people
Oral micronized progesterone peaked at levels not significantly different from mid-luteal levels, a 1985 study of 10 volunteers found. Nine were healthy postmenopausal women. One was a man. Each took a single dose. Blood progesterone peaked at 2.8 hours on average and fell to baseline within a day.
Key Findings
In nine healthy postmenopausal women and one man, blood progesterone reached its peak 2.8 ± 0.35 hours on average after a single oral dose.
Peak progesterone was not significantly different from mean mid-luteal levels in control cycles of seven healthy women with regular ovulatory cycles.
Every subject had a significant rise in progesterone over baseline. The rise lasted at least 6 hours, and levels were back at baseline by 24 hours.
Estradiol, FSH, LH, cortisol, aldosterone, lipids and liver enzymes stayed without significant change across the 24 hours of observation.
No major complications were reported during the 24 hours. Three women felt drowsy. One reported worse hot flashes at 24 hours. Stomach and bowel side effects were not reported in that time.
Interpretation
This 1985 study followed 10 volunteers through one oral dose of micronized progesterone. Blood was drawn over 24 hours. Peak progesterone levels matched average mid-luteal levels. Higher peaks went with higher estradiol in the five people already on estrogen therapy. Estradiol, FSH, LH, cortisol, aldosterone, lipids and liver enzymes showed no real change over the 24 hours. The authors say longer studies are needed to confirm how well this drug works over time, and its side effects. The findings support larger studies of oral micronized progesterone as a hormone therapy option.
RRM Context
RRM treats progesterone as the hormone made after ovulation. The corpus luteum makes it. This paper treats natural progesterone as different from synthetic progestins. Progestins can cause side effects, such as low mood and headaches.
Our editorial summary of this paper, not the article's abstract.
Abstract
Progesterone (P) has not been administered orally because of reportedly poor bioavailability and a rapid clearance rate. Unfortunately, the synthetic derivatives, although orally active, have a number of disadvantages and fail to mimic natural P completely. To investigate the bioavailability and short-term toxicity of oral micronized P, a standardized dose of 200 mg of micronized P was administered to nine healthy postmenopausal women and one male subject. Serial determinations of serum P concentrations demonstrated rapid absorption of P. Peak concentrations of P rose from a negligible baseline level to 17.0 +/- 4.9 ng/ml at an average of 2.8 +/- 0.35 hours after administration. The peak concentrations of P were equivalent to those observed in the midluteal phase in normal control cycles (14.1 +/- 2.7 ng/ml). All subjects exhibited significant elevation of P over baseline levels that persisted for at least 6 hours after the single oral dose and returned to initial levels by 24 hours. There was no significant change in estradiol, follicle-stimulating hormone, luteinizing hormone, cortisol, aldosterone, lipids, or hepatic enzymes during the 24-hour study interval.
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