Intervention: Progesterone
Trial phase: Phase 1
ATC code: G03DA04 | G03FA04
SMILES: [H][C@@]12CCC3=CC(=O)CC[C@]3(C)[C@@]1([H])CC[C@]1(C)[C@@H](C(C)=O)CC[C@@]21[H]
Sex: Female
Age groups: Adult
Healthy volunteers: Accepts Healthy Volunteers
Participants at risk: 4
Group description: Oral micronized progesterone (100 mg) suspension
Eligibility criteria:
Inclusion Criteria:

Subjects will be healthy women with regular menstrual cycles and no evidence of hyperandrogenism.
Subjects will be 18-30 years old; the investigators use a cutoff age of 30 years because age-related alterations in the hypothalamic-pituitary-ovarian axis is uncommon before age 30 years.
Subjects will be willing to strictly avoid pregnancy (using non-hormonal methods) during the time of study and must be willing and able to provide informed consent.

Exclusion Criteria:

Pregnancy
Lactation
History of allergy to progesterone
BMI < 18 kg/m2 or > 30 kg/m2 (underweight and obesity can affect hypothalamic-pituitary-ovarian function)
Excessive exercise, defined as routine and current engagement in either (a) moderate exercise (e.g., brisk walking) exceeding 14 hours per week or (a) vigorous exercise exceeding 7 hours a week.
Clinical hyperandrogenism (primarily hirsutism)
Abnormally elevated free testosterone or DHEAS concentration
A previous diagnosis of diabetes, a fasting glucose ≥ 126 mg/dl
Abnormal TSH (subjects with adequately treated hypothyroidism, reflected by normal TSH values, will not be excluded; or, for a new diagnosis of hypothyroidism, further study will at the least be delayed pending appropriate treatment) (confirmed on repeat)
Abnormal prolactin (confirmed on repeat)
Evidence of Cushing's syndrome by history or physical exam
History of venous thromboembolism, breast/ovarian/endometrial cancer
The investigators will exclude women with any other cancer diagnosis and/or treatment (with the exception of basal cell or squamous skin carcinoma) unless they have remained clinically disease free (based on appropriate surveillance) for five years.
Women with anemia (hematocrit < 36% and hemoglobin level < 12 g/dl) will be treated with iron for a maximum of 2 sequential months before the 1st admission and/or before the 2nd admission. If they remain anemic after 2 sequential months of ferrous gluconate (325 mg bid), they will then be excluded from further participation in the study.
Women with a significant history of cardiac or pulmonary dysfunction (e.g., known or suspected congestive heart failure; known or suspected coronary atherosclerosis; asthma requiring systemic intermittent corticosteroids; etc.) will be excluded.
Women with liver enzymes, alkaline phosphatase, or bilirubin > 1.5 times upper limit of normal (confirmed on repeat) will be excluded, with the exception that mild bilirubin elevations will be accepted in the setting of known Gilbert's syndrome.
Abnormal sodium or potassium concentrations (confirmed on repeat); bicarbonate concentrations <20 or >30 (confirmed on repeat)
Women with abnormal renal function (i.e., serum creatinine > 1.4) will be excluded (confirmed on repeat)
Due to the amount of blood being drawn in the study, subjects with body weight < 110 pounds will be excluded from the study
Being a study of the acute effects of progesterone on the hypothalamic-pituitary unit, subjects must not take hormonal medications (e.g., oral contraceptives) or other medications known to affect the reproductive axis for 60 days prior to the study and during the study.