🌹 Female Libido & Sexual Health

What this panel can settle, and by what logic

This panel settles the reversible contributors, which is a narrower claim than the one these tests are usually sold with, and a more useful one. Three of them.

1. Total Testosterone read against SHBG (Sex Hormone-Binding Globulin), not on its own. Most testosterone circulates bound to SHBG, so a total of 35 ng/dL with an SHBG of 130 nmol/L and the same total with an SHBG of 45 nmol/L are different physiological states. Free testosterone in women sits at concentrations where the calculation and the assay both matter, and the laboratory position statement on measuring sex steroids exists largely because of it Casals 2023. This is the pairing that makes the post-pill picture visible: a normal total with a high SHBG and a low free fraction.
2. Estradiol, Sensitive (LC/MS-MS) with LH & FSH separates perimenopause from suppression. A falling estradiol with a rising FSH is the menopausal transition; a low estradiol with low gonadotropins is central suppression and a different problem. Combined oral contraceptives act on this axis directly and by an amount that depends on the formulation: estradiol valerate with dienogest suppressed FSH by 27% (95% CI −51 to −3) against 64% for the ethinylestradiol version (95% CI −78 to −51, P = 0.04) Haverinen 2022.
3. Prolactin and TSH (Thyroid-Stimulating Hormone) catch two treatable suppressors. Hyperprolactinemia lowers desire directly, and hypothyroidism does it through fatigue. Ferritin and Vitamin D (25-Hydroxy) are on the list for the same reason: they flatten libido through exhaustion rather than through the gonadal axis Cancado 2025.

What it cannot settle, and what would

No testosterone concentration diagnoses low desire, and no guideline says otherwise. The ISSWSH clinical practice guideline for systemic testosterone in hypoactive sexual desire disorder is explicit that the diagnosis is clinical and that blood levels are not the diagnostic instrument Parish 2021. A free testosterone at the bottom of the female range is a finding to discuss; it is not the cause, and treating the number rather than the person is how women end up on doses aimed at a male reference interval.

Female testosterone assays are working at the edge of what they can do. Concentrations in women are roughly a twentieth of male ones, and immunoassays lose accuracy there, which is why the position statement on measuring sex steroids recommends mass spectrometry for low concentrations Casals 2023. A result of 18 ng/dL from an immunoassay and 11 ng/dL from LC-MS/MS may be the same woman on the same day.

A high Prolactin may not be a high prolactin. Macroprolactin, an inactive antibody-bound complex, accounts for around a fifth of hyperprolactinemia Sharma 2021, and prolactin assays cross-react with it to different degrees, which is exactly why screening policy is written per-assay Smith 2022.

And it cannot reach the causes that are not hormonal. Relationship context, depression, SSRIs, pain, pelvic floor dysfunction and vulvovaginal atrophy are all commoner than any pattern on this panel Parish 2021. A completely normal set of results does not mean nothing is wrong; it means the answer is somewhere a blood test does not go.

Draw conditions that decide whether the money is wasted

Four conditions, and the first two are the ones that decide whether the hormone half is readable at all.

1. Cycle days 2 to 5 if you are still cycling. Estradiol, Sensitive (LC/MS-MS) and LH & FSH swing across the cycle by more than most pathology moves them, so a day-20 estradiol and a day-3 estradiol are not comparable measurements Casals 2023.
2. Say what contraception you are on, on the form. A combined pill changes the answer rather than confounding it, and the size of the change depends on the estrogen: FSH suppression differed by more than twofold between two formulations in a head-to-head trial Haverinen 2022.
3. 7 to 10am. Testosterone and DHEA-S both follow a diurnal pattern, and at female concentrations an afternoon draw removes what little signal there was Casals 2023.
4. No biotin for 72 hours Li 2020. Prolactin, TSH, LH and FSH are streptavidin-based on the common analyzers, so one supplement moves four of these eight markers.

How you would know it answered your question, and what each pattern means next

Five patterns, and what each one changes.

• Normal Total Testosterone, high SHBG (Sex Hormone-Binding Globulin), low free testosterone, on the pill: the classic reversible picture. If you stop or switch, SHBG moves over months rather than weeks, so retest at 3 to 6 months and not before Haverinen 2022.
• Low Estradiol, Sensitive (LC/MS-MS) with a rising LH & FSH: perimenopause. That is a treatment conversation about estrogen, and local estrogen for dryness is a separate and highly effective one Parish 2021.
• Raised Prolactin: repeat it rested, then ask the laboratory to screen for macroprolactin before any imaging is booked Smith 2022.
• Ferritin under 30 ng/mL or TSH (Thyroid-Stimulating Hormone) above 4 mIU/L: fix these first and give it 12 weeks. Both flatten desire through fatigue, both are cheap, and neither needs a hormone specialist Cancado 2025.
• Everything normal: a common and honest result. The next step is a clinician who treats sexual health, not a repeat panel — and if testosterone is ever considered, the guideline's own position is that it is prescribed on symptoms, monitored to keep concentrations in the female physiological range, and reviewed at 3 to 6 months Parish 2021.

Sources read for these sections

• Parish SJ, et al. International Society for the Study of Women's Sexual Health Clinical Practice Guideline for the Use of Systemic Testosterone for Hypoactive Sexual Desire Disorder in Women. Journal of Sexual Medicine 2021 · PMID 33814355
• Casals G, et al. Recommendations for the measurement of sexual steroids in clinical practice. A position statement of SEQCML/SEEN/SEEP. Advances in Laboratory Medicine 2023 · PMID 37359897
• Haverinen A, et al. Estradiol Valerate vs Ethinylestradiol in Combined Oral Contraceptives: Effects on the Pituitary-Ovarian Axis. Journal of Clinical Endocrinology and Metabolism 2022 · PMID 35279718
• Sharma LK, et al. Prevalence of Macroprolactinemia in People Detected to Have Hyperprolactinemia. Journal of Laboratory Physicians 2021 · PMID 34975255
• Smith TP, et al. Cross-reactivity in assays for prolactin and optimum screening policy for macroprolactinaemia. Clinical Chemistry and Laboratory Medicine 2022 · PMID 35708266
• Cancado RD. Defining Global Thresholds for Serum Ferritin: A Challenging Mission in Establishing the Iron Deficiency Diagnosis in This Era of Striving for Health Equity. Diagnostics (Basel) 2025 · PMID 39941219
• Li D, Ferguson A, Cervinski MA, Lynch KL, Kyle PB. AACC Guidance Document on Biotin Interference in Laboratory Tests. J Appl Lab Med 2020 · PMID 32445355