Cortisone is a steroid hormone produced by your adrenal glands, but on its own it is biologically inactive. It functions as a precursor that your tissues convert into cortisol, the hormone that actually does the heavy lifting: regulating blood sugar, controlling inflammation, managing the stress response, and influencing everything from bone density to mood. When people refer to “cortisone” in a medical context, they often mean cortisol or one of the many synthetic corticosteroids modeled after it. Understanding what cortisone does requires understanding the conversion that activates it and the far-reaching effects of the cortisol it becomes.
How Cortisone Becomes Active
Cortisone circulates in your blood as an inactive molecule. It only becomes useful once an enzyme called 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) converts it into cortisol, the form that can bind to glucocorticoid receptors and trigger cellular responses.1PubMed. The cortisol-activating enzyme 11β-hydroxysteroid dehydrogenase type 1 in skeletal muscle in the pathogenesis of the metabolic syndrome This conversion happens locally in tissues rather than in one central location. Your liver, fat tissue, and skeletal muscle all contain 11β-HSD1, and the amount of enzyme present varies by tissue type and even by the size of individual fat cells. In adipose tissue, the enzyme’s activity correlates tightly with fat cell size, meaning larger fat deposits convert more cortisone to cortisol locally.2PubMed Central. Depot-specific Regulation of the Conversion of Cortisone to Cortisol in Human Adipose Tissue
This local conversion system is one reason cortisol’s effects are not uniform across the body. A tissue with abundant 11β-HSD1 will see more cortisol activity than one with less of the enzyme, even when circulating cortisone levels are the same everywhere. The same principle applies to synthetic corticosteroids used in medicine: cortisone acetate taken as a pill must be converted to cortisol before it works, whereas drugs like prednisolone are already in their active form.3Synapse (KoreaMed / KAMJE). Pharmacologic Characteristics of Corticosteroids
Raising Blood Sugar and Mobilizing Energy
Once cortisone has been converted to cortisol, one of its most immediate jobs is to keep blood sugar available. Cortisol pushes the liver to manufacture new glucose from non-sugar building blocks like amino acids and lactate, a process called gluconeogenesis. In a controlled experiment, a high dose of cortisol infused over four hours raised blood glucose and increased glucose production, with virtually all of that increase coming from ramped-up gluconeogenesis.4PubMed. Cortisol increases gluconeogenesis in humans: its role in the metabolic syndrome Cortisol also enhances the supply of raw materials the liver needs for this glucose manufacturing and helps shuttle those materials across cell membranes.5Endocrinology and Metabolism. Glucocorticoid-Induced Hyperglycemia: A Neglected Problem
At the same time, cortisol works against insulin in skeletal muscle. It blocks the transporter that normally pulls glucose out of the bloodstream and into muscle cells, effectively reducing how well muscles respond to insulin’s signal.5Endocrinology and Metabolism. Glucocorticoid-Induced Hyperglycemia: A Neglected Problem In everyday life, this system is useful: during a stressful event, your body needs quick energy in the blood rather than stored away in muscle. The problem arises when cortisol levels stay elevated for weeks or months, whether from chronic stress or from taking corticosteroid medications. Persistently high glucocorticoid activity can push blood sugar into diabetic territory, a side effect that clinicians sometimes underappreciate.
Dialing Down Inflammation
Cortisol is one of the body’s most powerful natural anti-inflammatory agents, and this is the property that made cortisone famous. In 1948, Philip Hench and Edward Kendall administered cortisone (then called “compound E”) to patients with severe rheumatoid arthritis and saw dramatic improvements. That work, along with Tadeus Reichstein’s research on adrenal hormones, earned all three the Nobel Prize in 1950.6PubMed. The History of Cortisone Discovery and Development
The anti-inflammatory mechanism centers on a molecular switch called NF-κB, which normally activates genes that drive inflammation. Cortisol suppresses this pathway, which in turn dials down the production of inflammatory proteins like the adhesion molecules that help immune cells swarm to an injury site.7PubMed. Glucocorticoid effects on NF-kappaB binding in the transcription of the ICAM-1 gene By dampening this cascade at the gene-expression level, cortisol can reduce swelling, redness, and pain in tissues throughout the body. It is a blunt but effective tool: rather than targeting one specific inflammatory molecule, it suppresses the master switch that controls many of them at once.
The Feedback Loop That Keeps It in Check
Your body does not just produce cortisol and let it accumulate. A tightly regulated feedback system runs from the hypothalamus in the brain down through the pituitary gland to the adrenal glands, often called the HPA axis. When cortisol levels rise high enough, cortisol itself signals the brain to stop calling for more. It does this by acting on glucocorticoid receptors in the hypothalamus, hippocampus, and pituitary, dampening the release of the signaling hormones that would otherwise keep the adrenals churning out cortisol.8PubMed Central. Regulation of the Hypothalamic-Pituitary-Adrenocortical Stress Response
This negative feedback is not just about ending a stress response. It also shapes the daily rhythm of cortisol release. Under normal conditions, cortisol peaks in the early morning and dips to its lowest point around midnight. The feedback loop fine-tunes these pulses so that cortisol is available when you need it and pulls back when you do not.9PubMed Central. Role of glucocorticoid negative feedback in the regulation of HPA axis pulsatility This rhythm matters clinically, as we will see in the section on timing doses of corticosteroid medications.
Cortisone Shots for Joint Pain
The most familiar encounter most people have with cortisone is a shot into an aching joint. These injections deliver a synthetic corticosteroid directly to the site of inflammation, providing localized relief without flooding the entire body with the drug. For osteoarthritis, the effect is real but modest and short-lived. Systematic reviews find that the pain relief typically lasts about two to four weeks on average when compared against a saline injection, and many patients end up getting repeat injections several times a year.10Osteoarthritis Imaging. Debate: Intra-articular steroid injections for osteoarthritis – harmful or helpful?
The duration of benefit depends heavily on the underlying condition. In a rheumatoid arthritis knee, pain relief lasted roughly eight weeks. In osteoarthritis, it was closer to three weeks. In contrast, children with juvenile idiopathic arthritis who received a knee injection stayed in remission for more than six months in the majority of cases, with a mean duration of over a year.11PubMed. Local effects of intra-articular corticosteroids Inflammatory conditions tend to respond better than wear-and-tear arthritis, which makes sense given that the drug’s primary action is suppressing inflammation.
There is a legitimate concern about repeated injections damaging the joint itself. In animal studies, corticosteroid-treated cartilage showed signs of necrosis that did not appear in cartilage treated with a non-steroidal anti-inflammatory or with nothing at all.12PubMed Central. The effect of local corticosteroid or ketorolac exposure on histologic and biomechanical properties of rabbit tendon and cartilage This is why most guidelines recommend limiting the number of injections per joint per year, even though the short-term pain relief can be meaningful.13PubMed Central. Intraarticular injections (corticosteroid, hyaluronic acid, platelet rich plasma) for the knee osteoarthritis
What Long-Term Glucocorticoid Use Does to Bones and Muscles
When corticosteroids are taken systemically for extended periods, the same properties that make them therapeutically powerful begin to cause damage. Bone is one of the first casualties. Glucocorticoids shift the behavior of the stem cells that would normally become bone-building cells, redirecting them toward other fates and shortening the lifespan of mature bone-building cells. The net result is a pronounced drop in new bone formation.14PubMed. Mechanisms of glucocorticoid-induced osteoporosis At the same time, glucocorticoids can stimulate the activity of bone-resorbing cells in the short term, creating a double hit: less bone being built, more being broken down.15Bone. Molecular mechanisms of glucocorticoid-induced osteoporosis Glucocorticoid-induced osteoporosis is one of the most common forms of secondary osteoporosis, and fractures can occur at bone density levels that would be considered relatively safe in someone not taking these drugs.
Muscles take a hit too. Glucocorticoids slow the transport of amino acids into muscle cells, decrease overall protein synthesis, and specifically reduce the production of key structural proteins in fast-twitch muscle fibers.16ScienceDirect. Glucocorticoid-Induced Muscle Atrophy: Mechanisms And Therapeutic Strategies People on long-term corticosteroids often notice weakness in the hips and thighs first, because those large muscles with a high proportion of fast-twitch fibers are especially vulnerable.
The Broader Side Effect Picture
Beyond bones and muscles, prolonged glucocorticoid exposure reshapes the body in ways that are sometimes visible from across a room. The classic Cushingoid appearance includes a round “moon face” and abdominal weight gain. In one clinical series, every patient with iatrogenic Cushing’s syndrome displayed moon face and central obesity.17PubMed Central. Different Potent Glucocorticoids, Different Routes of Exposure but the Same Result: Iatrogenic Cushing’s Syndrome and Adrenal Insufficiency Moon face is more than cosmetic: research has found it to be an independent predictor of developing glucocorticoid-induced diabetes, with roughly a sixfold increase in risk compared to patients taking similar doses who did not develop the facial changes.18Journal of the Endocrine Society. Moon-like Facies by Glucocorticoid Is Associated With The Development of Diabetes and Body Image Disturbance
The immune system also takes collateral damage. Chronic oral corticosteroid use depletes a specific subset of immune cells, leaving patients vulnerable to infections that healthy immune systems normally handle easily. At higher doses, the risk of opportunistic infections rises substantially, with Pneumocystis jirovecii pneumonia being one of the better-known dangers.19Annals of Allergy, Asthma & Immunology. Systemic Corticosteroids: Mechanisms of Action and Impact on Immune Function
Blood pressure is another concern. Cortisol can overstimulate receptors in the kidneys that cause sodium retention and fluid buildup, which increases blood volume and drives up blood pressure.20PubMed. Cortisol and the renal handling of electrolytes: role in glucocorticoid-induced hypertension and bone disease For someone already managing hypertension, adding a systemic corticosteroid can make control noticeably harder.
Effects on Mood and Sleep
Cortisol does not stop at the neck. It crosses into the brain and influences neurotransmitter systems that govern mood, anxiety, and sleep architecture. Corticosteroids alter levels of serotonin, dopamine, and glutamate, and these shifts are linked to structural changes in brain regions involved in emotional regulation, particularly the hippocampus and amygdala.21PubMed Central. Corticosteroid-Induced Psychiatric Disorders: Mechanisms, Outcomes, and Clinical Implications Clinically, patients on corticosteroids can experience anything from mild euphoria or irritability to full-blown psychosis, though severe psychiatric reactions are uncommon at lower doses.
Sleep is disrupted in a specific, measurable way. When healthy volunteers were given hydrocortisone, their rapid eye movement (REM) sleep decreased, and the sensitivity of certain serotonin receptors in the brain was blunted.22Journal of Affective Disorders. Effects of hydrocortisone on brain 5-HT function and sleep Interestingly, some of these effects overlap with what antidepressant drugs do, which may partly explain why short bursts of corticosteroids sometimes produce a temporary mood lift before the darker side effects set in with prolonged use.
Why You Cannot Just Stop Taking Corticosteroids
Remember the HPA axis feedback loop described earlier. When you take synthetic corticosteroids for an extended period, the constant supply of external glucocorticoids tells your brain there is no need to produce its own. The hypothalamus and pituitary dial back their signaling hormones, and the adrenal glands gradually shrink from disuse. If you abruptly stop taking the medication, your adrenals cannot ramp back up quickly enough to meet the body’s cortisol demands. The result is adrenal insufficiency: fatigue, weakness, low blood pressure, and in severe cases a life-threatening adrenal crisis.23BMJ. Glucocorticoid induced adrenal insufficiency
The risk depends on how long you have been on the medication, the dose, the potency of the specific drug, and individual variation in how sensitive your HPA axis is to suppression. Some people develop meaningful suppression after just a few weeks on moderate doses, while others tolerate longer courses with less trouble. Because of this unpredictability, the standard practice is to taper corticosteroids gradually rather than stopping cold. The taper gives the adrenal glands time to wake up and resume production. During the withdrawal period, some patients experience a “glucocorticoid withdrawal syndrome” with joint pain, fatigue, and general malaise that mimics a flare of whatever condition they were treating, which can make it psychologically difficult to continue reducing the dose.
Timing Doses to the Body’s Clock
Because cortisol follows a natural circadian rhythm, when you take a corticosteroid turns out to matter. In rheumatoid arthritis, the disease’s hallmark morning stiffness is driven by a surge in inflammatory cytokines that happens during the night. Taking a glucocorticoid first thing in the morning, which has been standard practice for decades, actually arrives too late to intercept that nocturnal inflammatory ramp-up. Research on timed-release formulations that deliver the drug in the early hours of the morning, before the inflammatory surge, has shown better control of morning stiffness than conventional morning dosing.24RMD Open. Glucocorticoids and chronotherapy in rheumatoid arthritis
Timing also affects side effects. Simulations of prednisolone dosing found that giving the drug around 6 AM produced the least suppression of the body’s own cortisol production. A small evening dose, by contrast, suppressed the natural cortisol rhythm more aggressively.25PubMed Central. Assessment of the impact of dosing time on the pharmacokinetics/pharmacodynamics of prednisolone This is why physicians generally recommend taking corticosteroids in the morning when possible: it aligns with the body’s own peak and causes less disruption to the HPA axis. The growing field of chronotherapy is trying to find even more precise timing windows that balance symptom control with minimal side effects.
Cortisone’s Role in Fetal Lung Development
One of the most important medical applications of corticosteroids has nothing to do with joint pain or autoimmune disease. When a baby is at risk of being born prematurely, physicians give the mother a course of corticosteroids to accelerate the development of the baby’s lungs. Premature lungs lack adequate surfactant, the slippery substance that keeps air sacs from collapsing with every breath. Corticosteroids stimulate the immature lung cells to ramp up surfactant production, which can mean the difference between a baby who breathes independently and one who needs intensive respiratory support.
Newer research using lab-on-a-chip systems that model the placenta and fetal lung together has started to examine exactly how much corticosteroid is optimal. These platforms have found that beyond a certain concentration, corticosteroids begin to damage placental cells without producing any additional surfactant benefit.26ScienceDirect. Understanding the impact of antenatal corticosteroids via placenta and fetal lung microphysiological analysis platform (MAP) on a chip Current guidelines on prenatal corticosteroids are based on relatively old clinical data, and this more granular biological research may eventually refine the recommended dosing to maximize lung maturation while minimizing harm to the placenta.
Eyes and Corticosteroids
A side effect that catches many patients off guard is the impact of corticosteroids on the eyes. Long-term use can raise the pressure inside the eye, increasing the risk of glaucoma, and can also accelerate cataract formation. The underlying reason has to do with how readily different corticosteroids accumulate in eye tissues. Research measuring how corticosteroids partition into the trabecular meshwork, the tissue responsible for draining fluid from the eye, found that more fat-soluble corticosteroids accumulated there in higher concentrations.27JAMA Ophthalmology. Trabecular Meshwork and Lens Partitioning of Corticosteroids: Implications for Elevated Intraocular Pressure and Cataracts This accumulation can impair drainage and push intraocular pressure upward. The risk applies to corticosteroids taken by mouth, inhaled, or applied directly to the eye as drops, though the degree of risk varies with the route and duration of use. Anyone on long-term corticosteroid therapy should have periodic eye pressure checks, even if they have no history of eye problems.