🔍 Low T? Rule Out the Reversible Causes First

What this panel can settle, and by what logic

Eleven markers, and this is the one list on the site that matches its own promise almost exactly. What it settles is which reversible cause you have, and three of the four this page claims are genuinely measurable here.

1. LH & FSH beside Total Testosterone is the discrimination the panel is built around. Low testosterone with a high LH is testicular and your own production is unlikely to return; low testosterone with a low or normal LH arises above the testis and is often reversible Livingston 2023. Exogenous testosterone suppresses LH within weeks, so this is a question with a deadline Desai 2022.
2. Fasting Insulin and HbA1c (Hemoglobin A1c) explain most low testosterone under 50. Visceral fat produces a functional hypogonadism in which total testosterone falls while LH and FSH stay in the normal range, and the size of the weight loss tracks the size of the recovery Wittert 2022. Weight loss is the first-line treatment for it Shenoy 2024, which no other panel on this site is equipped to show you.
3. Prolactin at $9 is the cheapest catch with the biggest consequence. A prolactin-secreting adenoma suppresses the whole axis and is treated medically rather than surgically Petersenn 2023. Roughly a fifth of raised prolactin results are macroprolactin, an inactive complex the assay counts and the body cannot use Sharma 2021.
4. Ferritin here is not an iron question. A high ferritin with a high transferrin saturation on the Iron Panel (Iron, TIBC, Transferrin Saturation) is the screen for iron overload, which causes hypogonadism by depositing iron in the pituitary and is one of the few causes whose treatment restores your own production Cancado 2025. Hereditary Hemochromatosis, DNA genotyping confirms it.

What it cannot settle, and what would

It names untreated sleep apnea as one of the four reversible causes it covers, and it contains no test for sleep apnea. There is no blood marker for obstructive sleep apnea at any price Platon 2023; a high hematocrit on the Complete Blood Count (CBC) with Differential is a hint, not a test. If you snore, wake unrefreshed, or have been told you stop breathing, the sleep study is the missing purchase and it is the one most likely to change the answer.

It cannot diagnose hypogonadism from this draw, because a diagnosis is symptoms plus two low morning values. Testosterone carries substantial within-subject biological variation Itkonen 2024, and both the laboratory position and the BSSM practice statements require the repeat before anyone treats Livingston 2023 Hackett 2023. The panel is bought once, so the second draw is a second purchase: budget it now rather than discover it.

A low LH is not evidence of a pituitary tumor, and that is the misreading this page most invites. In obesity-related secondary hypogonadism the gonadotropins sit in the normal range with a low testosterone Wittert 2022, which is far commoner than an adenoma and is treated with weight loss Shenoy 2024. Imaging belongs to a low testosterone with low gonadotropins plus a confirmed raised Prolactin, a visual field defect, or another pituitary hormone that is off Petersenn 2023.

And it cannot tell you whether testosterone therapy would help you. No value on this list predicts symptomatic response, which is why testosterone deficiency is defined as symptoms plus a repeatedly low morning concentration rather than as a number Hackett 2023.

Draw conditions that decide whether the money is wasted

The panel's own instruction is two morning draws. Here is what each condition costs when it is skipped.

1. 7 to 10am both times, fasted. Testosterone follows a diurnal rhythm and reads lower later in the day, which is the commonest route to a diagnosis a man does not have Livingston 2023. An afternoon value cannot be rescued by interpretation; it has to be drawn again.
2. Two separate days inside a fortnight, same laboratory, same method. The European biological variation study exists because one testosterone is not a stable quantity Itkonen 2024. This panel uses LC-MS/MS with equilibrium dialysis, which is the better method and is also not interchangeable with the direct free testosterone other panels report Livingston 2023.
3. Prolactin rested. It rises with stress, a difficult venepuncture and sleep, so sit quietly for 20 to 30 minutes first. If it comes back high, macroprolactin screening comes before any imaging Sharma 2021.
4. No biotin for 3 days, and no hCG, clomiphene, enclomiphene or anastrozole in the preceding 6 weeks. Biotin at 5,000 mcg and above shifts TSH, LH, FSH and prolactin together on streptavidin-based platforms Li 2020, and those four drugs move the exact numbers this panel exists to read.

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

Five patterns. Only one of them ends in a prescription.

• Low testosterone twice with a high LH & FSH: primary. Recovery of your own production is unlikely and the conversation is about replacement Livingston 2023. Book a semen analysis first if children are anywhere in the plan, because spermatogenesis recovery after stopping runs from months to years with no reliable predictor Desai 2022.
• Low testosterone with normal LH & FSH and a raised Fasting Insulin: obesity-related secondary hypogonadism. Treat the metabolism and retest at 6 months, not 6 weeks — the testosterone rise is proportional to the weight lost and weight is not lost in a month Wittert 2022 Shenoy 2024.
• Raised Prolactin: repeat it rested, then ask the laboratory to screen for macroprolactin Sharma 2021. Only a confirmed, genuinely raised prolactin goes to imaging Petersenn 2023.
• Ferritin above 300 ng/mL with a high saturation: screen for Hereditary Hemochromatosis, DNA before accepting therapy, because treating the iron can restore the axis on its own Cancado 2025.
• Everything normal and symptoms unchanged: the panel worked and the answer is elsewhere. The sleep study is the next purchase Platon 2023; repeating these 11 markers in 8 weeks will produce the same 11 numbers.

Sources read for these sections

• Livingston M, et al. Adult Male Hypogonadism: A Laboratory Medicine Perspective on Its Diagnosis and Management. Diagnostics (Basel) 2023 · PMID 38132234
• Wittert G, Grossmann M. Obesity, type 2 diabetes, and testosterone in ageing men. Reviews in Endocrine and Metabolic Disorders 2022 · PMID 35834069
• Shenoy MT, et al. Management of male obesity-related secondary hypogonadism: A clinical update. World Journal of Experimental Medicine 2024 · PMID 38948417
• Itkonen O, et al. The European biological variation study (EuBIVAS): Biological variation data for testosterone, follicle stimulating hormone, prolactin, luteinizing hormone and dehydroepiandrosterone sulfate in men. Clinica Chimica Acta 2024 · PMID 38341016
• Hackett G, et al. The British Society for Sexual Medicine Guidelines on Male Adult Testosterone Deficiency, with Statements for Practice. World Journal of Men's Health 2023 · PMID 36876744
• Platon AL, et al. An Update on Obstructive Sleep Apnea Syndrome-A Literature Review. Medicina (Kaunas) 2023 · PMID 37629749
• Sharma LK, et al. Prevalence of Macroprolactinemia in People Detected to Have Hyperprolactinemia. Journal of Laboratory Physicians 2021 · PMID 34975255
• Petersenn S, et al. Diagnosis and management of prolactin-secreting pituitary adenomas: a Pituitary Society international Consensus Statement. Nature Reviews Endocrinology 2023 · PMID 37670148
• Desai A, et al. Understanding and managing the suppression of spermatogenesis caused by testosterone replacement therapy (TRT) and anabolic-androgenic steroids (AAS). Therapeutic Advances in Urology 2022 · PMID 35783920
• 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