Synthetic data only. Never enter patient information; nothing is sent or stored. For clinicians. Not FDA cleared.For licensed clinicians. Educational demonstration on synthetic data. Never enter real patient identifiers or protected health information: everything runs in your browser and nothing is sent or stored. Clinical decision support only; not FDA cleared; physician review is required.
CPE-006 · version 1.0.0
Male Hypogonadism Pattern Engine: confirm low testosterone, classify it, and screen before any therapy
Symptoms plus low testosterone on two morning samples. The engine classifies, flags cautions, and never recommends starting therapy.
Low testosterone is a laboratory finding with a long list of non-specific symptoms. The Male Hypogonadism Pattern Engine follows the Endocrine Society and AUA approach: symptoms prompt a measurement, one low value is only a reason to repeat it, and the diagnosis needs symptoms plus an unequivocally low total testosterone on two fasting morning samples.
After that it asks what type of hypogonadism the pattern suggests, which reversible contributors are present, and which cautions would have to be resolved before any discussion of therapy. It will never tell a physician to start, stop or dose testosterone.
Playground
Load a synthetic case or type your own values. The result recomputes as you type, and every rule links to its page.
Testosterone and hormones
- <264
- 264–299
- 300–350 borderline
- >350
4.3 g/dL is assumed when left empty.
Symptoms and findings
Possible reversible contributors
Testosterone therapy context
What it does
- Treats one low value as unconfirmed and requires a second morning sample before the criteria are called met.
- Marks samples drawn in the afternoon, during acute illness or after high-dose biotin as provisional.
- Classifies primary versus secondary patterns from LH and FSH, and flags raised prolactin and possible pituitary mass effect.
- Calculates free testosterone with the Vermeulen equation, with no threshold applied.
- Screens the Endocrine Society's cautions to therapy and the monitoring prompts for hematocrit and PSA.
What it never does
- Recommend starting, continuing, stopping or dosing testosterone.
- Diagnose from symptoms alone.
- Call a prolactinoma, or tell a physician not to treat.
- Classify baseline hypogonadism while testosterone or anabolic steroids are being taken.
Safety gates
These gates run before the pattern is shown, and urgent findings are displayed first.
- Severe or new headache or visual field loss with low testosterone or raised prolactin raises an urgent alert.
- Fertility wishes raise a priority alert: testosterone suppresses spermatogenesis.
- Prostate or breast cancer, PSA above 4, hematocrit above 50%, untreated severe sleep apnea or a recent cardiovascular event raise a therapy-caution alert.
- Hematocrit above 54% on therapy raises a priority alert.
Inputs
- Total testosterone on up to two separate samples, SHBG, albumin
- LH, FSH, prolactin
- Symptoms and examination findings
- Reversible contributors and sample circumstances
- Therapy context, hematocrit, PSA, fertility wishes
Scope
In scope
- Adult men aged 18 and over
Routed out
- Patients under 18
The full rule catalog
20 active rules and 1 sandbox or context entries. Each has its own page with conditions, outputs and evidence. 21 of 21 active rules are exercised by at least one synthetic case.
Scope and validity
Diagnosis
Classification
Safety
Context triggers
Missing data
Calculations
Synthetic cases
Every case is synthetic. Open one to see the inputs, the full result and the rule trace; then change the values.
TESTO-FX-01
Low libido and erectile dysfunction, testosterone never measured
A 48-year-old with sexual symptoms and fatigue.
TESTO-FX-02
One low testosterone
Total testosterone 218 ng/dL on a single morning sample.
TESTO-FX-03
Low on two samples with a primary pattern
Testosterone 205 and 190 with LH 22 and FSH 31.
TESTO-FX-04
Secondary pattern with obesity and diabetes
LH 1.2 and FSH 2.0 with BMI 36.
TESTO-FX-05
Raised prolactin with low testosterone
Prolactin 95 ng/mL.
TESTO-FX-06
Headache, visual field loss and prolactin 310
Possible pituitary mass effect.
TESTO-FX-07
Borderline total testosterone
Total testosterone 320 with SHBG 62 and symptoms.
TESTO-FX-08
Normal testosterone with fatigue and low mood
A 45-year-old with total testosterone 520.
TESTO-FX-09
Afternoon sample
Testosterone 240 drawn at 3 pm.
TESTO-FX-10
Two low values during acute illness
Both samples were drawn while the patient was in hospital.
TESTO-FX-11
Chronic opioid use
Testosterone 210 and 200 with a low-normal LH.
TESTO-FX-12
Fertility desired
Low testosterone in a man trying to conceive.
TESTO-FX-13
Therapy under consideration: hematocrit 52% and PSA 5.2
Cautions to review before any decision.
TESTO-FX-14
On therapy with hematocrit 56.1%
Monitoring flags the raised hematocrit.
TESTO-FX-15
On therapy, monitoring overdue
Hematocrit last checked 18 months ago, no PSA on record.
TESTO-FX-16
Anabolic steroid use
Testosterone 30 and LH below 0.2.
TESTO-FX-17
Low testosterone with osteoporosis
A fragility fracture and two low values.
TESTO-FX-18
A 16-year-old is outside the adult pathway
Adolescent patient.
TESTO-FX-19
Confirmed low, gonadotropins missing
The type of hypogonadism cannot be classified yet.
TESTO-FX-20
Two samples that disagree
280 ng/dL, then 410 ng/dL.
TESTO-FX-21
No symptoms and no result
Nothing to classify.
TESTO-FX-22
Two low values, no symptoms
A biochemical finding without compatible symptoms.
TESTO-FX-23
Primary pattern with Klinefelter features
Small testes and tall stature.
TESTO-FX-24
Therapy under consideration with untreated sleep apnea
A caution to resolve first.
TESTO-FX-25
Normal testosterone, no symptoms
Total testosterone 600.
Evidence
Guidelines and references the rules cite. Each rule page lists the ones that support it.
EV-ES-TRT-2018Bhasin S, Brito JP, Cunningham GR, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2018;103(5):1715-1744.
Supports: Diagnose with symptoms plus unequivocally low testosterone on two morning fasting samples Contraindications and cautions to therapy; monitoring of hematocrit and PSA Evaluation of the type of hypogonadism with LH and FSH
EV-AUA-2018Mulhall JP, Trost LW, Brannigan RE, et al. Evaluation and Management of Testosterone Deficiency: AUA Guideline. J Urol. 2018;200(2):423-432.
Supports: Total testosterone below 300 ng/dL as the threshold; repeat and confirm; fertility counselling before therapy
EV-TRAVISON-2017Travison TG, Vesper HW, Orwoll E, et al. Harmonized reference ranges for circulating testosterone levels in men of four cohort studies in the United States and Europe. J Clin Endocrinol Metab. 2017;102(4):1161-1173.
Supports: Lower limit of 264 ng/dL in healthy young men
EV-VERMEULEN-1999Vermeulen A, Verdonck L, Kaufman JM. A critical evaluation of simple methods for the estimation of free testosterone in serum. J Clin Endocrinol Metab. 1999;84(10):3666-3672.
Supports: Calculated free testosterone from total testosterone, SHBG and albumin
EV-ES-PRL-2011Melmed S, Casanueva FF, Hoffman AR, et al. Diagnosis and treatment of hyperprolactinemia: an Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2011;96(2):273-288.
Supports: Causes of raised prolactin, including drugs and macroprolactin; when to image the pituitary
EV-TRAVERSE-2023Lincoff AM, Bhasin S, Flevaris P, et al. Cardiovascular Safety of Testosterone-Replacement Therapy. N Engl J Med. 2023;389(2):107-117.
Supports: Cardiovascular safety data in hypogonadal men at increased cardiovascular risk, with higher rates of atrial fibrillation, pulmonary embolism and acute kidney injury
Frequently asked questions
What counts as low testosterone?
The AUA uses total testosterone below 300 ng/dL; the Endocrine Society's harmonized lower limit for healthy young men is 264 ng/dL. The engine uses 300 and notes when a value falls between 264 and 299. In either case a single value is not enough: it must be confirmed on a separate fasting morning sample.
Does the engine recommend testosterone therapy?
No. It never recommends starting, continuing, stopping or dosing therapy. It lists the cautions that would have to be resolved first, and monitoring prompts for men already on therapy.
How does it tell primary from secondary hypogonadism?
LH and FSH. Raised gonadotropins with low testosterone point to the testes; a low or inappropriately normal LH points to the hypothalamus, pituitary or functional suppression. Prolactin and the reversible contributors are checked in the same step.
Why is free testosterone shown without a cutoff?
Free testosterone calculated with the Vermeulen equation depends on assay performance and on assumed albumin, and published cutoffs vary. The number is there to inform judgment when SHBG is abnormal, not to classify.
What does the engine do with a raised prolactin?
It raises a priority alert and suggests considering pituitary imaging and reviewing drugs, hypothyroidism, renal failure and macroprolactinemia, in line with the Endocrine Society hyperprolactinemia guideline. It does not name a prolactinoma.
Specification status: Executable specification v1.0.0, authored by Biod from the narrative CPE-006 specification and current guidelines. Reviewed by Dr. Vinicius Amaral, D.O. Not for clinical production use.
Clinical review: Dr. Vinicius Amaral, D.O., Medical reviewer, 2026-10-03.
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CPE-008
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Game
Pattern challenge
Guess what the engine will report.
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