Which hormonal laboratory tests should be ordered to evaluate a woman's endocrine status?

Hormonal Laboratory Testing for Women's Endocrine Evaluation

For comprehensive evaluation of a woman's hormonal status, order TSH, free T4, FSH, LH, estradiol, progesterone, and prolactin, with timing critically dependent on menstrual cycle phase and clinical indication. 1

Core Hormone Panel

The essential hormonal assessment includes:

• TSH and free T4 for thyroid function evaluation 2, 1
• FSH and LH for pituitary-gonadal axis assessment 1
• Estradiol for ovarian function 1
• Progesterone for ovulation confirmation 3
• Prolactin for hyperprolactinemia screening 1

Critical Timing Requirements

For Premenopausal Women with Regular Cycles

Baseline assessment must occur during the early follicular phase (cycle days 2-5) to obtain accurate FSH, LH, and estradiol measurements. 1, 3 This timing is essential because:

• FSH and LH levels vary significantly throughout the menstrual cycle 4
• Early follicular phase represents hormonal baseline when levels are most interpretable 3
• Measurements outside this window can lead to incorrect conclusions 1

For the most accurate FSH and LH assessment, collect three samples 20 minutes apart and average the results. 3

For Ovulation Confirmation

Mid-luteal progesterone (approximately 7 days after suspected ovulation) is the most reliable hormonal indicator of ovulation. 3 Progesterone levels <6 nmol/L indicate anovulation, while levels ≥6 nmol/L confirm ovulation occurred. 3

Optimal Collection Time

Morning collection around 8 AM is critical for accurate interpretation, particularly for ACTH and cortisol, though this timing also optimizes gonadotropin and sex hormone measurements. 1 This is especially important when evaluating hypogonadism, as testosterone shows significant diurnal variation. 1

Interpretation Framework

Distinguishing Primary vs. Secondary Hypogonadism

FSH and LH must be interpreted together with estradiol: 1

• Low gonadotropins (FSH/LH) with low estradiol = central/pituitary dysfunction 1
• High gonadotropins with low estradiol = primary ovarian failure 1
• FSH >35 IU/L and LH >11 IU/L suggest ovarian failure 3

PCOS Pattern Recognition

LH:FSH ratio >2 is characteristic of polycystic ovary syndrome and suggests anovulation. 1, 3 Women with PCOS typically show hypersecretion of LH with hypofunction of the FSH-granulosa cell axis. 3

Hypothalamic Dysfunction

LH <7 IU/mL may indicate hypothalamic dysfunction. 3 In functional hypothalamic amenorrhea, the LH:FSH ratio is typically <1 in approximately 82% of patients. 1

Special Clinical Situations

Irregular or Absent Cycles

For women with irregular cycles, anti-Müllerian hormone (AMH) can be used for assessment as it does not vary by menstrual day and is not affected by exogenous estrogen or progesterone. 3

Medication Considerations

Women on hormonal contraceptives must discontinue them at least 2 months before testing to allow return of normal pituitary-ovarian axis function. 3 Testing should be performed prior to steroid administration when evaluating for hypophysitis, as corticosteroids suppress the hypothalamic-pituitary axis. 1

Postmenopausal Women

For postmenopausal women, cycle timing is irrelevant, but morning collection remains optimal. 1

Common Pitfalls to Avoid

• Single time-point measurements are inadequate for investigating reproductive disorders 1
• Normal baseline FSH, LH, and estradiol do not guarantee ovulation - mid-luteal progesterone is essential for confirmation 3
• PCOS patients may show normal FSH and estradiol but have elevated LH:FSH ratio, indicating anovulation despite seemingly normal individual values 3
• Timing errors are the most common mistake - measurements must occur on cycle days 3-6 specifically for baseline assessment 3

When to Expand Testing

Additional evaluation is warranted despite normal hormones if: 3

• Menstrual irregularity persists
• Infertility after 12 months of unprotected intercourse
• Clinical signs suggest endocrine disorder

In these cases, include thyroid function testing, prolactin measurement, and mid-luteal progesterone to confirm ovulation and rule out underlying endocrine disorders. 3