Why these six categories matter
Start with the clinical context, then interpret the number.
HRT-FET timing and safety depend on endocrine and metabolic health, thrombotic risk, the uterus and endometrium, infection status, and prior treatment history. The treating team selects tests from symptoms, history, local requirements and clinic protocol; there is no one mandatory panel for every patient.
Thyroid function
TSH, FT4 and antibodies: interpret the result in its clinical and laboratory context.
Current recommendations are not uniform. The 2024 ASRM guideline advises using laboratory- and age-specific TSH upper limits for nonpregnant patients attempting pregnancy; when those limits are unavailable, it uses 4.12 mIU/L. It does not support treating a TSH of 2.5–4.0 mIU/L solely to improve fertility or pregnancy outcomes.
A result must still be interpreted with symptoms, FT4, prior thyroid disease, medication, pregnancy status and the treating clinic’s protocol. Pregnancy-specific ranges apply after conception.
1.1 TSH: avoid a universal 2.5 cutoff
A TSH of 2.5–4.0 mIU/L is not, by itself, evidence that an HRT-FET cycle should be delayed or that levothyroxine is needed. Values above the laboratory upper limit require clinical review; overt hypothyroidism and markedly elevated TSH warrant endocrinology-led treatment.
1.2 FT4 and antibodies
- Normal FT4 with TSH above the applicable laboratory range suggests subclinical hypothyroidism and needs individualized review rather than automatic treatment.
- Low FT4 requires clinical assessment even when TSH is not elevated.
- Positive TPO-Ab or TG-Ab with otherwise normal thyroid function is not, by itself, a reason to postpone the cycle.
1.3 Thyroid antibodies
The TABLET trial found no live-birth benefit from levothyroxine in euthyroid women with positive TPO antibodies. Testing and treatment decisions should therefore be based on the full thyroid picture and individual risk factors, not antibody positivity alone.
| Dimension | Needs treatment or specialist review | Needs individualized review | Usually reassuring |
|---|---|---|---|
| TSH | Marked elevation or overt hypothyroidism | Above the applicable laboratory or age-specific upper limit | Within the applicable laboratory range; 2.5–4.0 alone is not a treatment trigger |
| FT4 | Below range: clinical or endocrine review | Near the lower limit: interpret with TSH and symptoms | Within range |
| TPO/TG-Ab | — | Positive with abnormal thyroid function | Positive with normal thyroid function: individualized follow-up |
Prolactin
A PRL result does not, by itself, diagnose pituitary disease.
Stress, sampling conditions, recent stimulation, medication, thyroid function and macroprolactin can all affect the result. Assays and reference ranges also differ, so fixed PRL bands should not decide whether a patient can proceed or must have MRI.
2.1 Confirm persistence and clinical relevance
The clinician may repeat a sample under standardized conditions, review medication and physiological causes, and assess macroprolactin when appropriate. Pituitary MRI depends on the degree and persistence of elevation, menstrual or ovulatory change, galactorrhea, headache, visual symptoms and other findings—not one global threshold.
2.2 Distinguish baseline from on-treatment results
Estrogen regimens can affect PRL. Baseline and on-treatment values should not be compared mechanically; the treating clinician decides the sampling point and whether repeat testing is useful.
| Situation | Clinical focus | Principle |
|---|---|---|
| One elevated result without symptoms | Sampling, medication, physiological causes and laboratory range | Clinician decides whether a standardized repeat is needed |
| Persistent elevation or symptoms | True PRL, thyroid function and pituitary features | Endocrine review; MRI only when clinically indicated |
| Change after HRT starts | Compare with baseline and protocol | Do not use one result as a universal cancellation rule |
Coagulation and thrombosis risk
Testing should follow individual thrombotic risk, not a universal panel.
Exogenous estrogen can affect thrombotic risk, but prior venous thrombosis, family history, obesity, smoking, immobility, comorbidity, dose and route also matter. These factors determine whether coagulation tests, D-dimer, antiphospholipid antibodies or specialist review are appropriate.
3.1 D-dimer and homocysteine are not stand-alone entry tests
D-dimer changes with infection, inflammation, pregnancy, recent procedures and many other conditions. Homocysteine is influenced by nutrition, renal function, medication and assay method. Neither has a universal HRT-FET red/amber/green cutoff, and neither should trigger self-directed anticoagulation or supplementation.
3.2 Antiphospholipid antibody positivity is not the same as APS
Antiphospholipid syndrome requires formal clinical and persistent laboratory criteria. One low-titer or isolated positive result does not establish APS. A reproductive clinician, hematologist or rheumatologist decides whether testing, repeat testing or a protocol change is indicated.
Glucose and lipid metabolism
The aim is pregnancy safety and management of established disease—not one perfect metabolic number.
Whether BMI, glucose, HbA1c, lipids or blood pressure need review depends on diabetes history, PCOS, cardiovascular risk, medication and the clinic’s safety policy. Established diabetes or a substantial metabolic concern warrants a preconception plan with the relevant clinician.
4.1 HOMA-IR has no universal entry cutoff
HOMA-IR varies by population, assay and sampling conditions. One fixed value should not cancel an HRT-FET cycle. Metformin should not be prescribed simply to make HOMA-IR “pass”; its use depends on a defined indication, contraindications, expected benefit and the treating clinician’s plan.
Uterus and endometrial conditions
Ultrasound findings must be read with cavity anatomy, history, embryo factors and protocol.
Transvaginal ultrasound is commonly the starting point. Symptoms, prior uterine procedures, repeated failure, suspected polyps or fibroids, adhesions, cesarean scar niche, cavity fluid or hydrosalpinx determine whether hysteroscopy, MRI or other evaluation is appropriate.
5.1 Endometrial thickness is not one universal pass line
Seven, eight or nine millimetres should not be presented as global entry cutoffs. Thickness has a continuous relationship with outcome, while timing, image quality, pattern, cavity findings, prior response, embryo factors and clinic protocol affect the decision. One thinner measurement should not automatically cancel a cycle without that context.
5.2 Cavity findings require individualized review
A polyp, fibroid, adhesion, uterine anomaly, scar niche or fluid does not automatically mean surgery. The reproductive team considers location, cavity distortion, persistence, symptoms and prior outcomes before recommending repeat imaging, hysteroscopy, treatment or continuation.
Infection and immune screening
Testing, treatment and retesting depend on the organism and the patient’s situation.
Whether syphilis, HIV, HBV, HCV, chlamydia or other tests are required depends on local law, the receiving clinic and individual risk. HPV, TORCH, vaginal microbiome and other panels should not be described as a mandatory universal HRT-FET bundle. Symptoms, vaccination and immunity history, pregnancy status and clinic protocol guide selection.
6.1 Chlamydia treatment and test-of-cure are not one-size-fits-all
A confirmed infection requires clinician-directed treatment and attention to partners and reinfection. Treatment and follow-up depend on pregnancy, adherence, persistent symptoms and suspected reinfection. CDC test-of-cure recommendations differ for pregnant and nonpregnant patients, so no fixed course or universal four-week-negative rule belongs here.
6.2 Mycoplasma species require different reasoning
Detection of Ureaplasma or Mycoplasma hominis should not automatically trigger antibiotics or a universal PCR-negative entry requirement without symptoms, inflammatory findings, specimen context and applicable local guidance.
6.3 Trichomoniasis, BV and candidiasis
Women with trichomoniasis should receive the current CDC-recommended regimen, with partner management and follow-up considered as appropriate; this page does not provide a dose or fixed course. BV and candidiasis treatment depends on symptoms, diagnosis, pregnancy status and clinician assessment.
6.4 Immune tests are not “the more, the better”
ESHRE does not support routine NK-cell activity, Th1/Th2 ratios or broad cytokine testing as entry requirements. ANA, antiphospholipid and thyroid antibody tests also need a clinical indication and should not be converted into automatic cycle-cancellation or immune-treatment rules.
Integrated decision-making
The final decision comes from the full record and treating team—not a cutoff chart.
A safer workflow is to identify findings needing prompt or specialist review, findings needing contextual review, and cases with no identified issue that can proceed under the clinic protocol. These are communication paths, not global entry grades.
Baseline and in-cycle results also cannot be mixed. Estrogen, progesterone, infection, recent procedures and pregnancy status can change several measures. The clinician needs the sampling date, medication and symptom history before deciding whether to repeat, modify or delay.
Official guidelines and sources
- ASRM: Subclinical hypothyroidism in the infertile female population (2024).
- ESHRE: Good practice recommendations on recurrent implantation failure.
- Endocrine Society: Diagnosis and treatment of hyperprolactinemia.
- NICE NG257: Fertility problems—assessment and treatment.
- CDC: Mycoplasma genitalium treatment guideline.
- CDC: Trichomoniasis treatment guideline.
- CDC: Chlamydial infections treatment and follow-up guideline.
Need help interpreting HRT-cycle screening results?
This article is for education and clinical communication only. Cycle entry and medication decisions should be made by a reproductive physician with full records.