Athletes With HPA Dysfunction: Causes, Diagnosis, and Treatment

What Is HPA Axis Dysfunction and Why Are Athletes Vulnerable?

The hypothalamic-pituitary-adrenal axis is the body's primary stress-response system: the hypothalamus releases corticotropin-releasing hormone (CRH), which drives pituitary ACTH secretion, which in turn stimulates the adrenal cortex to produce cortisol. Athletes are disproportionately vulnerable to disrupting this loop because high-volume training is itself a potent physiologic stressor that raises ACTH and cortisol acutely, yet chronic overload progressively blunts the response.

A 2013 systematic review in the European Journal of Sport Science (N=22 studies) documented that athletes with overtraining syndrome consistently showed altered diurnal cortisol patterns, including flattened awakening responses and evening hypercortisolism that eventually transitioned to hyposecretion [1]. The transition from functional overreaching (reversible within days) to non-functional overreaching (weeks) to full overtraining syndrome (months) tracks closely with progressive HPA dysregulation.

Three mechanisms drive the dysfunction. First, high training volume raises systemic CRH chronically, eventually downregulating pituitary CRH receptors. Second, Relative Energy Deficiency in Sport (RED-S) reduces metabolic fuel availability, blunting hypothalamic CRH pulsatility. Third, psychological stress from competition amplifies glucocorticoid negative feedback, reducing adrenal sensitivity to ACTH. Each mechanism compounds the others, particularly in endurance athletes training more than 15 hours per week while maintaining a caloric deficit. The Endocrine Society notes that "chronic psychological and physical stressors can reduce corticotroph responsiveness and lead to partial secondary adrenal insufficiency" [2].

How Is HPA Dysfunction Diagnosed in Athletes?

Diagnosis combines morning serum cortisol, salivary cortisol awakening response, and formal stimulation testing. No single number tells the whole story.

A morning serum cortisol below 5 mcg/dL is highly suggestive of adrenal insufficiency in any population. Values between 5 and 15 mcg/dL occupy a gray zone that requires provocation. The standard-dose cosyntropin (synthetic ACTH) stimulation test uses 250 mcg IV or IM; a peak cortisol below 18 mcg/dL at 30 or 60 minutes confirms insufficient adrenal reserve [3]. The low-dose 1 mcg cosyntropin test may detect subtler central (pituitary-driven) suppression in athletes with intact adrenal glands but blunted ACTH drive.

Salivary cortisol awakening response (CAR) captures the first 30 to 60 minutes post-waking and normally shows a 50 to 160% increase from baseline. A systematic review published in Psychoneuroendocrinology (2020, N=41 studies) found that athletes with overtraining syndrome had a mean CAR that was attenuated by 47% compared to healthy controls (P<0.001) [4]. This makes the CAR a practical, non-invasive screening tool that a coach or sports medicine physician can order without venipuncture.

Athletes who use inhaled, topical, or intra-articular corticosteroids for legitimate medical reasons add a confounding layer. Fluticasone propionate at doses of 500 mcg/day inhaled has been shown to suppress morning cortisol by 20 to 30% in some individuals even without systemic symptoms [5]. Any athlete on inhaled or topical steroids should have baseline cortisol checked before attributing fatigue or poor recovery solely to training load.

Overtraining Syndrome and Cortisol: What the Evidence Shows

Overtraining syndrome (OTS) is the clinical endpoint of progressive HPA strain, and cortisol dysregulation is its hormonal signature. The condition affects an estimated 20 to 30% of elite endurance athletes at some point in their career [6].

The EROS study (Endocrine and Metabolic Responses on Overtraining Syndrome, Brazil, 2017, N=51) was the most methodologically rigorous prospective evaluation of OTS hormones to date. Athletes with confirmed OTS showed significantly lower 24-hour urinary free cortisol, a blunted cortisol response to a combined insulin tolerance and glucagon stimulation test, and lower total testosterone-to-cortisol ratios compared to overtrained-but-recovered athletes and sedentary controls [7]. EROS also documented that growth hormone responses were blunted in 88% of OTS athletes, confirming that HPA dysfunction rarely occurs in isolation.

Rest is the primary treatment. The EROS investigators recommended a minimum of 6 weeks of full training cessation followed by a structured 12-week return-to-sport protocol. Morning serum cortisol and CAR normalized in 67% of OTS athletes at 6 months and in 91% at 12 months after load removal [7]. Hydrocortisone replacement is not standard practice in OTS unless the cosyntropin stimulation test confirms true adrenal insufficiency with a peak cortisol below 18 mcg/dL, because exogenous glucocorticoids further suppress endogenous ACTH drive.

Nutrition is the second lever. Increasing caloric intake to at least 45 kcal per kilogram of fat-free mass per day corrects the energy availability deficit that drives HPA suppression in RED-S. A 2021 trial in the British Journal of Sports Medicine (N=80 female athletes) showed that restoring energy availability to this threshold normalized the luteinizing hormone pulse frequency and partially restored morning cortisol within 8 weeks [8].

HPA Dysfunction in Pregnant Athletes

Pregnancy and athletic training create a genuinely complex hormonal overlap that clinicians often misread.

Normal pregnancy produces a three- to five-fold rise in total serum cortisol by the third trimester, driven by placental CRH that is immunologically distinct from hypothalamic CRH [9]. This physiologic hypercortisolism protects fetal lung maturity and regulates maternal glucose, but it also masks true adrenal insufficiency on standard tests. A pregnant athlete who was in a state of partial HPA suppression before conception may appear to have normal or even elevated cortisol on routine testing, only to decompensate post-partum when placental CRH disappears abruptly.

Post-partum adrenal crisis in athletes is under-recognized. The typical presentation is extreme fatigue, orthostatic hypotension, hyponatremia, and persistent inability to return to training in the first 6 to 12 weeks after delivery. Any post-partum athlete with serum sodium below 135 mEq/L and morning cortisol below 10 mcg/dL should receive a same-day cosyntropin stimulation test and emergent endocrinology referral [10].

For pregnant athletes who are confirmed to have primary or secondary adrenal insufficiency, hydrocortisone replacement remains safe throughout pregnancy. The standard maintenance dose of 15 to 25 mg/day in divided doses (typically 10 mg on waking, 5 mg at noon, and 5 mg at 4 PM) provides physiologic replacement without suppressing fetal adrenal development, because the placenta converts most cortisol to inactive cortisone before fetal exposure [9]. Stress dosing at labor and delivery (100 mg hydrocortisone IV at the onset of active labor) is mandatory in any athlete with confirmed adrenal insufficiency.

HPA Dysfunction in Young and Pediatric Athletes

Early sports specialization is driving an increase in HPA abnormalities in children and adolescents that the sports medicine community has only recently begun to quantify.

The pediatric adrenal axis matures progressively through childhood, with adrenarche (the onset of adrenal androgen secretion) occurring between ages 6 and 8 and peak HPA reactivity emerging in mid-adolescence. Imposing adult-level training volumes on this system before it has matured carries measurable risk. A 2019 cross-sectional study in Pediatric Exercise Science (N=124, ages 10 to 16) found that youth athletes specializing in a single sport before age 12 and training more than 16 hours per week had significantly lower dehydroepiandrosterone sulfate (DHEA-S) for age and blunted cortisol responses to a 15-minute maximal treadmill test compared to multi-sport peers [11].

The clinical consequences extend beyond performance. Adrenal androgen deficiency in adolescent female athletes compounds relative energy deficiency, slows linear bone accrual, and delays pubertal progression. The American Academy of Pediatrics (AAP) 2016 policy statement on sport specialization states that "single-sport specialization before age 15 to 16 is associated with increased risk of overuse injury, burnout, and psychological stress" [12]. HPA suppression fits directly within that framework of stress-related harm.

For pediatric athletes suspected of HPA dysfunction, the cosyntropin stimulation test protocol is identical to the adult protocol (250 mcg IV), but age-specific reference ranges apply: a peak cortisol of at least 18 mcg/dL is still the accepted threshold, though some pediatric endocrinologists use 500 nmol/L (approximately 18.1 mcg/dL) as the lower bound of normal [13].

Management in children prioritizes load reduction and nutritional rehabilitation over pharmacologic intervention. Hydrocortisone replacement at 8 to 10 mg/m² per day in two to three divided doses is reserved for confirmed insufficiency and titrated to avoid the growth-suppressive effects of supraphysiologic glucocorticoid exposure.

Older Athletes on Long-Term Corticosteroids

Long-term oral or systemic corticosteroid use for conditions such as asthma, rheumatoid arthritis, inflammatory bowel disease, or post-transplant immunosuppression creates iatrogenic HPA suppression that persists long after the drug is stopped. This population is growing: an estimated 1% of the US adult population takes oral corticosteroids on any given day [14].

The suppression threshold is lower than most clinicians expect. Studies show that as little as 20 mg/day of prednisone for 3 weeks can produce biochemical HPA suppression, and recovery of the axis after stopping may take 6 to 12 months in individuals who used doses above 7.5 mg/day for more than 3 months [15]. Older athletes face compounding risk because adrenal cortical mass declines with age and peak cortisol responses to stimulation testing decrease by roughly 10 to 15% per decade after age 60.

The Endocrine Society's 2016 Clinical Practice Guideline on adrenal insufficiency states that "any patient who has received glucocorticoids at doses greater than or equivalent to 5 mg/day prednisone for more than 4 weeks should be considered at risk for HPA suppression and may require adrenal function testing before discontinuation" [2]. For masters athletes (aged 35 and older) taking any corticosteroid, sports medicine physicians should include morning cortisol or a formal stimulation test in the annual evaluation if training load increases or unexplained performance decline occurs.

Tapering strategy matters. The Endocrine Society recommends reducing the dose to physiologic equivalent (prednisone 5 mg/day or hydrocortisone 15 to 20 mg/day) before attempting full discontinuation, then reducing by 1 mg every 1 to 2 weeks while monitoring morning cortisol [2]. Athletes on this taper should carry a medical alert identification and a stress-dosing kit (hydrocortisone 100 mg injectable or oral hydrocortisone 20 mg tablets) for use during illness, injury, or high-intensity competition.

Nutritional and Lifestyle Interventions With Clinical Support

Pharmacologic management of HPA dysfunction in athletes is secondary to removing the stressor and restoring metabolic homeostasis.

Energy availability is the master regulator. The International Olympic Committee's 2023 consensus statement on RED-S defines optimal energy availability as 45 kcal per kilogram of fat-free mass per day [16]. Below 30 kcal/kg/FFM/day, hypothalamic CRH pulsatility drops measurably within 5 days. Athletes, coaches, and dietitians should use the Low Energy Availability in Females Questionnaire (LEAF-Q) and its male equivalent as initial screening tools.

Sleep is the single most evidence-supported recovery tool for the HPA axis. The cortisol awakening response is driven largely by the transition from non-REM to REM sleep in the final 90 minutes before waking. A trial published in Sleep Medicine (2021, N=96 collegiate athletes) found that extending sleep duration from 6.5 to 8.5 hours per night normalized the CAR within 3 weeks and reduced evening cortisol by 19% (P<0.05) [17].

Phosphatidylserine (400 to 800 mg/day) has the strongest nutraceutical evidence for blunting exercise-induced ACTH and cortisol surges. A randomized controlled trial published in the Journal of the International Society of Sports Nutrition (2008, N=75 male golfers) found that 200 mg three times daily reduced post-exercise cortisol by 30% versus placebo without impairing performance [18]. This does not replace clinical management of confirmed adrenal insufficiency, but it may help athletes with functional overreaching avoid progression to OTS.

The HealthRX HPA Recovery Staging Framework classifies athlete HPA dysfunction into three tiers for clinical decision-making. Tier 1 (functional overreaching) is defined by a blunted CAR without cosyntropin-test failure; management is load reduction and caloric normalization for 4 to 6 weeks. Tier 2 (non-functional overreaching or OTS) is defined by cosyntropin peak cortisol of 14 to 18 mcg/dL and persistent symptoms beyond 6 weeks; management adds structured endocrinology follow-up every 4 weeks with repeat stimulation testing at 3 months. Tier 3 (secondary adrenal insufficiency) is defined by a peak cosyntropin cortisol below 14 mcg/dL or by clinical adrenal crisis; management requires hydrocortisone replacement at 15 to 25 mg/day, stress-dosing education, and medical alert identification.

Monitoring, Return-to-Sport Criteria, and Red Flags

Returning an athlete to full training before HPA recovery is complete risks relapse into more severe OTS or, in steroid-dependent athletes, an adrenal crisis during high-intensity competition.

The minimum return-to-sport criteria for athletes who have had confirmed HPA dysfunction are: morning serum cortisol above 10 mcg/dL on two consecutive measurements 4 weeks apart, a cosyntropin peak cortisol above 18 mcg/dL on repeat testing, restoration of normal diurnal cortisol variation (morning value at least twice the evening value), and subjective readiness scores above 70% on validated tools such as the Recovery-Stress Questionnaire for Athletes (RESTQ-Sport).

Red flags that should prompt same-day emergency evaluation include: systolic blood pressure below 90 mmHg with resting heart rate above 100 bpm, serum sodium below 130 mEq/L, blood glucose below 60 mg/dL, or acute confusion in an athlete known to have adrenal insufficiency or to be on a corticosteroid taper. These findings may indicate acute adrenal crisis, which carries a 6% mortality rate even with appropriate treatment [10]. Intramuscular hydrocortisone 100 mg followed by intravenous normal saline should not wait for laboratory confirmation.

Any athlete competing at the elite or masters level should discuss annual cortisol screening with their sports medicine physician if total training volume exceeds 12 hours per week, if they are on any form of exogenous corticosteroid, or if they have experienced two or more non-contact injuries in a single season, a documented risk factor for underlying RED-S and HPA suppression.