Male Athlete Testosterone Panel Interpretation: Total T, Free T, SHBG, and the RED-S vs Overtraining Syndrome vs Hypogonadism Differential in the Sports Nutrition Intake

A 34-year-old competitive road cyclist shows up at intake three weeks after his primary care physician handed him a bloodwork panel with a total testosterone of 312 ng/dL, a note reading "low — consider referral for TRT evaluation," and a recommendation to schedule a consultation with a men's-health clinic. He has been racing at a regional-elite level for eight years, his training week has held at 15-18 hours across the past 12 months, his weight has drifted from 71 kg to 68 kg over that same window as he has "leaned out for climbing season," his resting heart rate is 44 bpm, and his power at threshold is up 4% year-over-year despite a self-reported energy intake of 2,900 kcal/day and a body mass index of 21.1. His libido has been noticeably suppressed for the past six months. His morning erections are gone. His mood has flattened. He sleeps eight hours a night but wakes tired. He is in your office because before he lets a men's health clinic write him a testosterone prescription he wants a second opinion on whether the low number is a diagnosis or a signal.\n\nThe testosterone number in isolation is not the diagnosis. It is a variable at the end of a hypothalamic-pituitary-gonadal axis that responds to caloric availability, training load, sleep, body composition, recovery status, and psychological stress on a timescale of weeks to months. A total testosterone of 312 ng/dL in a hard-training endurance athlete with a suppressed body mass, a suppressed libido, and a flattened mood is not the same clinical case as a total testosterone of 312 ng/dL in a sedentary 34-year-old with a normal BMI and normal energy availability. The men's-health-clinic pathway treats the number; the sports nutrition intake works the differential. Sometimes the answer is "this is RED-S masquerading as hypogonadism, and the treatment is caloric restoration, not exogenous testosterone." Sometimes the answer is "this is a genuine primary or secondary hypogonadism that warrants endocrine referral." The workup separates them.\n\nThis post is the male-athlete testosterone workup I run when the primary-care panel flags a low number and the clinical picture — training load, energy availability, body composition trajectory, symptom cluster, sleep, mood — deserves the follow-on before any pharmacologic decision is made. The six-dimension interpretive frame, the free T and SHBG follow-on the total number misses, the LH/FSH differential that separates primary from secondary suppression, the energy-availability and training-load overlay, the four-quadrant clinical matrix, the medical-coordination triggers, the common counseling mistakes, and the SOAP pattern that documents the case defensibly.\n\n## Why total testosterone alone under-differentiates the athletic case\n\nThree structural reasons the standard reading collapses on the athlete.\n\nTotal testosterone measures bound plus free hormone, and SHBG shifts the ratio meaningfully in the athletic population. Sex hormone binding globulin binds testosterone and pulls it out of the biologically active pool. Endurance training, low energy availability, and a lean body mass all drive SHBG upward. A total T of 350 ng/dL paired with an SHBG of 55 nmol/L reads as a very different case than a total T of 350 ng/dL paired with an SHBG of 25 nmol/L — the calculated or measured free testosterone in the high-SHBG athlete may be substantially lower than the same total value in a sedentary reference. Reading total T without the SHBG context misreads the free-hormone story in the exact population where SHBG runs high.\n\nThe reference range was built against a sedentary distribution. Standard testosterone reference ranges reflect the general adult male population, which is heavily sedentary, heavier, and less lean than the endurance-athlete distribution. The "low" flag threshold is not calibrated against what a lean, well-fueled, well-recovered endurance athlete's testosterone should sit at. A number at the low end of the sedentary reference may still be low for the athletic case — or it may reflect a lean-body-mass and low-body-fat physiology where a lower testosterone reflects the physiologic set point rather than a pathology.\n\nA single-draw total T does not distinguish physiologic suppression from primary or secondary hypogonadism. The 34-year-old cyclist's low number could be low-energy-availability driven, overtraining-syndrome driven, primary testicular failure, secondary hypothalamic or pituitary suppression, or a mix. The single number carries none of that differential. The LH and FSH follow-on separates central (secondary) from primary suppression; the energy availability and training load overlay separates functional from structural. Without the follow-on, the number reads as "low" and the workup stops.\n\n## The six-dimension male-athlete testosterone workup\n\nDimension 1: Read total T against free T and SHBG, not in isolation. Order the full panel: total testosterone, free testosterone (calculated or measured), sex hormone binding globulin, and albumin (needed for the free T calculation if not measured directly). The free T is the biologically active hormone; SHBG shifts the total-to-free ratio in the athletic population; the total number alone in a high-SHBG athlete misreads the free hormone. Reference ranges for free T vary by lab and assay; a calculated free T under roughly 6.5 ng/dL is broadly consistent with low free hormone in the adult male, though the athletic reference distribution is not well characterized. Where the primary care panel returned total T only, request the free T and SHBG follow-on before any pharmacologic decision.\n\nDimension 2: Read LH and FSH to separate primary from secondary suppression. Luteinizing hormone drives testicular testosterone production; follicle stimulating hormone drives spermatogenesis. In primary hypogonadism (testicular failure), LH and FSH are elevated as the pituitary compensates for the failed downstream target. In secondary hypogonadism (hypothalamic or pituitary suppression), LH and FSH are inappropriately low or normal for the low testosterone. Functional suppression driven by low energy availability, overtraining, or high stress typically presents as secondary — LH is low or low-normal, FSH is low or low-normal, testosterone is low. Distinguishing structural secondary hypogonadism (pituitary adenoma, hypothalamic disorder) from functional secondary hypogonadism (RED-S, overtraining syndrome) requires the additional workup: prolactin, morning cortisol, thyroid panel, and imaging when structural cause is suspected. Reading LH and FSH is the branch point between the RD workup and the endocrine referral.\n\nDimension 3: Read against the energy availability overlay. Energy availability — dietary energy intake minus exercise energy expenditure, normalized to fat-free mass — is the single largest driver of functional hypothalamic-pituitary-gonadal suppression in the male athlete. Low energy availability (broadly, sustained EA under 30 kcal/kg FFM/day, though the male threshold is less precisely defined than the female) drives LH pulse-frequency suppression, testosterone suppression, and the RED-S clinical syndrome. The 34-year-old cyclist with an 18-hour training week and a self-reported 2,900 kcal/day intake may be sitting at an energy availability under 20 kcal/kg FFM/day depending on his fat-free mass and his true exercise energy expenditure — a chronic deficit large enough to explain the testosterone number entirely without invoking primary or structural pathology. Calculate the EA. Estimate the exercise energy expenditure with the same rigor the training-plan design uses. Read the testosterone number against the calculated EA before treating it as a diagnosis.\n\nDimension 4: Read against the training load and overtraining overlay. Chronic overtraining syndrome — a maladaptive response to a sustained training-load-recovery mismatch — presents with a cluster including performance stagnation or decline, elevated resting heart rate (or paradoxically depressed in some presentations), mood suppression, sleep disturbance, appetite changes, and endocrine shifts including testosterone suppression, cortisol dysregulation, and elevated inflammatory markers. The overtraining picture overlaps substantially with the RED-S picture — both present with functional secondary testosterone suppression — but the primary driver differs. RED-S is driven by energy deficit; overtraining is driven by training-load overload with or without adequate energy availability. Capture the acute-to-chronic workload ratio, the training-load trajectory over 12 weeks, the intensity distribution, the recovery-metric trajectory (heart rate variability, resting heart rate trend, subjective wellness), the performance-trajectory data, and the presence or absence of adequate deload weeks. The athlete with rising training load, minimal deload, and testosterone suppression sits in a different intervention frame than the athlete with stable training load, adequate deload, and a suppressed T driven by fueling shortfall.\n\nDimension 5: Read against the body composition and body mass trajectory overlay. Rapid unintentional weight loss, sustained low body fat (under approximately 8% in the endurance athlete range where it is even feasible), or a sustained body mass drift downward across the past 6-12 months is a substantial signal for the low-EA-driven case. The 34-year-old cyclist's drift from 71 kg to 68 kg over 12 months in the setting of increased training volume is a 4% body-mass loss that in the leaning-out narrative reads as intentional and adaptive, but in the fueling-shortfall narrative reads as under-supported adaptation. DEXA (where available) surfaces the fat-mass and lean-mass compartments directly — a lean-mass loss alongside the body-mass drift is a strong signal for the caloric-deficit-driven case; a fat-mass loss with lean-mass preservation is the target of the intentional leaning-out narrative. The body composition read paired with the testosterone number sharpens the differential.\n\nDimension 6: Read against the symptom cluster and history overlay. The RED-S / functional hypogonadism symptom cluster in the male athlete includes suppressed libido, loss of morning erections, mood suppression or depression, sleep disturbance, elevated injury or illness rate, stress-fracture history, prolonged recovery from routine sessions, plateaued or declining performance, cold intolerance, GI complaints, and cognitive slowing. Capture the trajectory — when did each symptom start, how has each progressed, what changed in training or fueling in the preceding window. Personal history of anabolic steroid use (past or current) is a critical differential — post-AAS hypogonadotropic hypogonadism can persist for months to years after cessation and mimics functional suppression on the panel. Family history of endocrine disorder, testicular history (undescended, torsion, trauma, orchitis), medication history (opioids, glucocorticoids, ketoconazole, spironolactone, and others suppress testosterone), and psychosocial stress load all belong in the read.\n\n## The four-quadrant clinical decision matrix\n\nThe six dimensions collapse into a four-quadrant matrix that drives the action plan.\n\nQuadrant 1: Total T within reference, free T within reference, SHBG in expected athletic range, LH and FSH within reference, energy availability adequate, no red-flag symptoms. The panel reads as compatible with normal athletic physiology. Document the integrated read; monitor at annual cadence or as symptoms arise.\n\nQuadrant 2: Total T low or low-normal, free T low-normal, LH and FSH low or low-normal (secondary suppression pattern), energy availability calculated as low, body-mass trajectory downward, symptom cluster present. The pattern is consistent with functional secondary hypogonadism driven by RED-S, overtraining syndrome, or both. The intervention pathway is caloric restoration, training-load recalibration, sleep and recovery optimization, and repeat panel at 12-16 weeks. Do not refer for pharmacologic testosterone treatment until the functional workup has been executed and the repeat panel drawn. The clinical error mode is treating the functional case as a structural one and starting exogenous testosterone in an athlete whose HPT axis would recover with caloric restoration — exogenous testosterone in this case suppresses the axis further, produces exogenous-dependent hypogonadism, and destroys the diagnostic clarity of future panels.\n\nQuadrant 3: Total T low, free T low, LH and FSH elevated (primary suppression pattern), or LH/FSH inappropriately low with structural red flags (visual field changes, headaches, galactorrhea, personal history suggestive of pituitary or testicular pathology). Endocrine referral is the primary action. The RD role is the co-management of the nutrition plan within the endocrine workup framework.\n\nQuadrant 4: Ambiguous panel, mixed signals, or the functional-vs-structural differential cannot be resolved on the initial workup. Order the extended follow-on — prolactin, estradiol, TSH and free T4, morning cortisol, DHEA-S, IGF-1, and (where indicated by the picture) semen analysis, ferritin, and iron studies. Coordinate with the primary care physician on the extended panel and, where relevant, endocrinology for the imaging or specialized workup.\n\n## The RED-S vs overtraining vs hypogonadism differential\n\nThe three functional presentations overlap on the initial panel. The distinguishing features:\n\nRED-S signals. Low energy availability calculated directly (dietary intake minus exercise energy expenditure per kg FFM). Body-mass or lean-mass trajectory downward across the recent window. Cold intolerance. Bone-stress-injury history or current low bone mineral density on DEXA. Suppressed resting metabolic rate on measured RMR relative to predicted. Iron-status shortfall commonly co-occurring. GI complaints. Restrictive eating patterns or disordered-eating red flags. Improvement in symptoms and panel values follows caloric restoration on a 12-16 week timescale.\n\nOvertraining syndrome signals. Sustained training-load overload without adequate deload. Performance decline despite maintained or increased volume. Elevated resting heart rate (or paradoxically depressed). Heart rate variability trending downward across 8+ weeks. Sleep disturbance without a clear behavioral cause. Mood suppression. Elevated inflammatory markers where measured. Improvement follows structured deload and training-load restoration on a 4-12 week timescale.\n\nPrimary hypogonadism signals. Elevated LH and FSH with low testosterone. Testicular history (undescended, torsion, trauma, orchitis, chemotherapy exposure, radiation exposure). Cryptorchidism history. Small testicular volume on exam. Karyotype disorders (Klinefelter and variants). Elevated FSH driven by seminiferous-tubule failure with or without Leydig-cell failure. Intervention is endocrine — the RD role is co-management.\n\nSecondary structural hypogonadism signals. Low LH and FSH with low testosterone and structural red flags — visual field changes, headaches, galactorrhea, hyperprolactinemia, other pituitary-hormone abnormalities. Head trauma or infection history. Pituitary imaging warranted. Endocrine referral is primary.\n\nPost-AAS hypogonadotropic hypogonadism. Personal history of anabolic steroid use, prohormone use, SARMs, or other exogenous androgen exposure. Presents as low LH and FSH with low testosterone, indistinguishable on the initial panel from the RED-S or overtraining case. The history is the diagnostic key. Recovery timescale varies widely and often warrants endocrine co-management.\n\n## When to refer to medical\n\nFive signals warrant medical referral beyond the dietetic workup.\n\nElevated LH and FSH with low testosterone. Primary hypogonadism pattern. Endocrine referral.\n\nStructural red flags — visual field changes, headaches, galactorrhea, hyperprolactinemia, other pituitary abnormalities. Secondary structural workup. Endocrine and neuro imaging referral as indicated.\n\nPersonal history of anabolic steroid, prohormone, or SARM use. Post-exposure hypogonadism warrants endocrine co-management on a timescale that outstrips the routine RD follow-up.\n\nPersistent low panel after 12-16 weeks of documented caloric restoration and training-load recalibration. The functional-workup non-responder warrants the structural workup.\n\nAny concurrent finding suggesting a structural or systemic cause — testicular exam abnormality, unexplained anemia, unexplained thyroid dysfunction, elevated prolactin, elevated hemoglobin A1c, or any of the RED-S-associated complications requiring medical management.\n\n## Common counseling mistakes\n\nReading total T alone and calling the case low. The high-SHBG athletic case where free T is preserved is under-differentiated by the total number. The low-SHBG case where free T is meaningfully low despite a total in the low-normal range is under-differentiated in the other direction. Order the full panel.\n\nFailing to calculate energy availability before endorsing a testosterone diagnosis. The 34-year-old cyclist with an 18-hour training week and a 2,900 kcal/day intake is likely sitting under 25-30 kcal/kg FFM/day depending on the exercise energy expenditure — a strong prior for the functional case. The dietetic workup that does not run the EA calculation misses the primary differential.\n\nEndorsing exogenous testosterone treatment for the functional case. Exogenous testosterone in a functionally suppressed HPT axis further suppresses LH and FSH, produces exogenous-dependent hypogonadism, and eliminates the diagnostic value of future panels. The functional case should be treated with caloric restoration, training-load recalibration, sleep and recovery optimization, and repeat panel at 12-16 weeks before any pharmacologic decision.\n\nIgnoring the anabolic-steroid or SARM history. Athletes commonly under-report exogenous androgen exposure. The history question needs to be direct and non-judgmental, and the differential shifts substantially on any positive.\n\nMissing the co-occurring RED-S complications. The low-T athletic case commonly co-occurs with iron shortfall, bone mineral density concerns, RMR suppression, GI complaints, and disordered-eating patterns. Screening the extended RED-S surface at intake catches the case as a syndrome rather than as an isolated hormone number. See the [low-energy-availability screening protocol](/blog/screening-athletes-for-low-energy-availability), the [iron-status workup](/blog/iron-status-workup-in-female-athletes) (the male version follows the same protocol), and the [bone-mineral-density workup](/blog/bone-mineral-density-workup-sports-dietetics).\n\nFailing to document the differential defensibly. The chart that records "low T, referred for medical" without the differential reasoning does not defend against a later question of why the RED-S or overtraining workup was not run. Document the four-quadrant assignment and the reasoning behind the pathway chosen.\n\n## Where this lands in the SOAP\n\nSubjective section format:\n\n```\nMale-Athlete Testosterone Workup (panel reviewed YYYY-MM-DD):\n- Total testosterone: [X ng/dL, morning draw Y AM]\n- Free testosterone: [X ng/dL or NOT ORDERED — flag]\n- SHBG: [X nmol/L or NOT ORDERED]\n- Albumin: [X g/dL, for free T calculation]\n- LH: [X IU/L or NOT ORDERED — flag]\n- FSH: [X IU/L or NOT ORDERED]\n- Prolactin: [X ng/mL or NOT ORDERED]\n- Morning cortisol: [X µg/dL]\n- TSH, free T4: [values]\n- Estradiol: [X pg/mL, if ordered]\n\nEnergy-availability and training context:\n- Training hours per week (past 4, past 12): [X, X]\n- Weekly training stress score or equivalent: [X]\n- Deload cadence past 12 weeks: [narrative]\n- Self-reported energy intake: [X kcal/day, method]\n- Estimated exercise energy expenditure: [X kcal/day, method]\n- Fat-free mass estimate: [X kg, DEXA / BIA / anthropometric]\n- Calculated energy availability: [X kcal/kg FFM/day]\n- EA category: [adequate / suboptimal / low]\n\nBody composition and trajectory:\n- Height / current mass / BMI: [values]\n- Body-mass trajectory past 12 months: [narrative]\n- Estimated body fat %: [X, method]\n- DEXA lean and fat mass (if available): [values]\n\nSymptom and history:\n- Libido: [normal / suppressed — trajectory]\n- Morning erections: [normal / absent — trajectory]\n- Mood: [normal / suppressed — trajectory]\n- Sleep quality: [narrative]\n- Recovery-metric trajectory (RHR, HRV, wellness): [narrative]\n- Injury / illness / stress-fracture history: [narrative]\n- AAS / prohormone / SARM history: [direct question, positive / negative / declines to answer]\n- Medications suppressing T: [list]\n- Testicular / endocrine / medical history: [narrative]\n\nQuadrant: [1-4 from clinical matrix]\nClinical impression: [statement integrating total T with free T / SHBG, LH/FSH primary-vs-secondary read, energy availability, training and body-composition overlay, symptom cluster, and history]\nAction: [free T / SHBG follow-on order / LH-FSH order / dietetic intervention / training-load recalibration / medical referral / observation]\nFollow-up: [recheck date, plan, escalation triggers]\n```\n\nAssessment integrates the six-dimension read and assigns the case to a quadrant. Plan documents the differential, the dietetic and training-load intervention (Quadrant 2), the medical-coordination communications (Quadrants 3 and 4), and the recheck cadence. See [SOAP notes for sports dietitians](/blog/soap-notes-for-sports-dietitians) for the broader documentation framework and [RED-S in male athletes](/blog/red-s-in-male-athletes-clinical-differential) for the related differential.\n\n## The Quadrant 2 dietetic intervention\n\nThe functional-suppression case in the male athlete responds to a 12-16 week structured intervention with three primary levers.\n\nCaloric restoration. Restore energy availability to at least 40 kcal/kg FFM/day sustained across the intervention window. For the 34-year-old cyclist at a calculated 22 kcal/kg FFM/day, this is a substantial upward shift in dietary energy — 800-1,200 kcal/day increase or more depending on the true expenditure estimate. Progressive over 2-4 weeks to permit GI adaptation. Weight regain is expected and is a signal of the intervention working; the athlete's frame around body-mass gain needs to be part of the counseling conversation, not an afterthought.\n\nTraining-load recalibration. Coordinate with the coach on a training-load reduction sufficient to shift the load-recovery balance. Deload cadence, session intensity distribution, and volume all sit in the coach's decision surface, but the RD role is surfacing the pattern and the direction. In the overtraining-dominant case, the training-load lever moves the panel; in the low-EA-dominant case, the caloric-restoration lever moves it; in the mixed case, both.\n\nSleep, recovery, and stress lever. Sleep restriction independently suppresses testosterone. Psychosocial stress independently suppresses testosterone. The intervention that treats the case as a pure caloric problem and does not surface the sleep and stress axis misses two of the largest levers. Screen at every visit and document the trajectory.\n\nThe repeat panel at 12-16 weeks — total T, free T, SHBG, LH, FSH, and any co-occurring markers — is the empirical validation of the intervention. Movement in the panel confirms the functional case; failure to move warrants the structural workup and the endocrine referral.\n\n## The masters-athlete trajectory\n\nTestosterone declines with age at approximately 1-2% per year after the fourth decade, but the trajectory is highly individual and the age-related decline overlaps with the training-load and energy-availability trajectory across a career. The masters athlete with a suppressed panel warrants the same six-dimension workup as the 34-year-old case, with the additional consideration that the age-related decline sits in the read as a baseline downward shift that does not by itself warrant treatment. The intervention framework is the same; the reference expectations sit slightly lower.\n\n## Where platform tooling helps\n\nThe bottleneck in the male-athlete testosterone workup at scale is the multi-system integration — the total T read against free T and SHBG, the LH and FSH separating primary from secondary, the energy availability calculation, the training-load trajectory, the body-composition and symptom overlays, the differential across RED-S, overtraining, and structural hypogonadism, the recheck cadence, the medical-coordination communications. The intake that runs the integration by hand drops it on busy weeks; the functional case gets referred prematurely for pharmacologic treatment, or the structural case gets held in the dietetic workup past the point where the endocrine referral should have happened.\n\nThe leverage is a male-athlete testosterone workup module that ingests total T, prompts for free T and SHBG follow-on, prompts for LH and FSH, calculates energy availability from intake and expenditure inputs, captures the training-load and body-composition trajectory, surfaces the four-quadrant decision matrix, pre-populates the SOAP documentation, tracks the 12-16 week recheck cadence, and manages the medical-coordination communications when referral is warranted. The RD's job is the clinical judgment and the conversation with the athlete, not the spreadsheet.\n\nThe chart trail is defensible — every interpretation tied to the integration context that justified it, every referral documented with the pattern that drove it, every dietetic intervention paired with the differential reasoning behind it.\n\n## The bottom line\n\nA low testosterone number on a primary-care panel in a male athlete is not a diagnosis. It is a variable at the end of an axis that responds to energy availability, training load, sleep, body composition, and psychosocial stress on a timescale of weeks to months. The workup that reads the total number in isolation and refers straight to a men's-health-clinic pharmacologic pathway misses the substantial subset of cases where the primary driver is fueling shortfall, training-load overload, or a mix — and where exogenous testosterone would treat the number by destroying the axis that would otherwise recover.\n\nThe workup that catches the functional case reads total T against free T and SHBG, orders LH and FSH to separate primary from secondary suppression, calculates energy availability, tracks the training-load and body-composition trajectory, integrates the symptom cluster and history, and assigns the case to a four-quadrant matrix that drives the intervention pathway. The Quadrant 2 case gets caloric restoration, training-load recalibration, sleep and stress work, and a repeat panel at 12-16 weeks. The Quadrant 3 case gets the endocrine referral early. The Quadrant 4 case gets the extended follow-on. The Quadrant 1 case gets documented as physiologic and monitored.\n\nThe 34-year-old cyclist with the 312 ng/dL total T, the 18-hour training week, the 2,900 kcal/day intake, the 4% body-mass drift, the suppressed libido, the missing morning erections, the flattened mood, and the primary-care recommendation for TRT consultation is not a case the men's-health-clinic pharmacologic pathway serves. He is a Quadrant 2 case pending the free T, SHBG, LH, and FSH follow-on, and the intake that runs the structured workup catches the difference. The intake that reads the total T and endorses the referral does not.\n\n[Calsanova's Dietitian plan](/signup?role=dietitian) ships a male-athlete testosterone workup module with panel ingestion, free T calculation, energy availability calculation, training-load and body-composition trajectory tracking, four-quadrant decision matrix, SOAP pre-population, and medical-coordination communications built in. The clinical judgment stays with the RD; the integration stays off the spreadsheet.