Rezdiffra (Resmetirom) Geriatric (65+): School and Activity Considerations

What Is Resmetirom and Why Older Adults Are the Core Patient Group

Resmetirom targets the thyroid hormone receptor beta (THR-beta) isoform expressed predominantly in the liver. By activating THR-beta, the drug reduces hepatic fat accumulation, lowers LDL-cholesterol, and reduces fibrosis-driving inflammatory signaling, all without meaningful thyroid hormone effects on the heart or bone that would come from systemic thyroid activation. [1]

Adults 65 and older carry a disproportionate burden of MASH. The condition's natural history spans two to three decades from early steatosis to cirrhosis, meaning many patients who reach fibrosis stages F2 or F3 are in their sixth or seventh decade of life. [2] Population data from the CDC show that prevalence of nonalcoholic fatty liver disease (the older umbrella term) rises with age and with the metabolic comorbidities, including type 2 diabetes and dyslipidemia, that cluster in older cohorts. [3]

The MAESTRO-NASH Trial and Its Geriatric Subgroup

MAESTRO-NASH enrolled 966 adults with biopsy-confirmed MASH and F2 or F3 fibrosis. [4] At 52 weeks, resmetirom 100 mg produced MASH resolution (defined as NAS ≥2 reduction without fibrosis worsening) in 25.9% of participants versus 14.2% placebo (P<0.001). Fibrosis improvement by at least one stage occurred in 24.2% versus 14.2% placebo. [4] Approximately 18% of the enrolled cohort was aged 65 or older, and the FDA review noted no statistically significant heterogeneity in efficacy by age subgroup. [5]

How Aging Changes Resmetirom Pharmacokinetics

No dose adjustment is formally required by age alone according to the Rezdiffra prescribing information. [5] Resmetirom is primarily metabolized by CYP2C8 and, to a lesser extent, CYP3A4, with a half-life of roughly 10 hours. Older adults commonly show reduced hepatic blood flow and lower CYP enzyme activity, which may increase drug exposure by 20 to 30% compared with younger adults, although this range is inferred from hepatic function analyses in the label rather than a dedicated geriatric pharmacokinetic study. [5] Clinicians should review the full medication list because common geriatric polypharmacy agents such as gemfibrozil (a strong CYP2C8 inhibitor) are contraindicated with resmetirom. [5]

Activity and Exercise: What the Evidence Supports in MASH Patients Over 65

Physical activity is one of the strongest non-pharmacological interventions for liver fat reduction in MASH, and it does not conflict with resmetirom's mechanism of action. The two approaches work through distinct but complementary pathways. [6]

Aerobic Exercise Targets in Older Adults on Resmetirom

The American Heart Association recommends 150 minutes per week of moderate-intensity aerobic activity for adults of all ages, including those with chronic liver disease, when cardiac and musculoskeletal status permits. [7] For geriatric MASH patients on resmetirom, the practical starting point is 20 to 30 minutes of brisk walking five days per week, titrated upward based on tolerance over four to six weeks.

A meta-analysis of 12 randomized controlled trials (total N=626) published in the Journal of Hepatology found that aerobic exercise reduced liver fat content by a mean of 3.5 percentage points as measured by MRI-PDFF versus inactive controls, independent of body weight change. [6] Resmetirom, in the MAESTRO-NASH extension cohort, reduced mean liver fat by approximately 37% from baseline (MRI-PDFF) at 52 weeks. [4] The two effects may be additive, though a dedicated exercise-plus-resmetirom trial has not yet been published.

Resistance and Balance Training

Sarcopenia affects up to 30% of community-dwelling adults over 70 and directly worsens the frailty trajectory in liver disease. [8] A 2022 study in older NAFLD patients (mean age 68, N=102) published in Hepatology Communications showed that 12 weeks of progressive resistance training three times per week reduced liver stiffness by 8.4% and improved grip strength by 4.1 kg versus controls. [9] Resmetirom's prescribing information does not contraindicate resistance training, but myopathy surveillance is warranted given that most MASH patients over 65 are also on statins, and resmetirom can modestly increase statin plasma levels through shared hepatic transporter pathways (OATP1B1/OATP1B3 inhibition). [5]

Muscle cramping or new-onset weakness in a geriatric patient on resmetirom plus a statin should prompt a serum CK measurement. The FDA label identifies rhabdomyolysis as a potential risk requiring clinical monitoring. [5]

Flexibility, Falls Prevention, and Low-Impact Programs

Falls are the leading cause of injury-related death in adults over 65 in the United States, with approximately 36 million falls reported annually per CDC data. [10] Low-impact programs such as tai chi, water aerobics, and chair yoga are appropriate first-line activity recommendations for frail older adults beginning resmetirom. These programs preserve functional mobility without imposing the hepatic or cardiac stress of high-intensity interval training.

The Otago Exercise Programme, validated in multiple randomized trials, reduces falls in adults over 65 by 35% over 12 months. [11] It requires no equipment, can be self-administered at home, and is compatible with the fatigue that some patients experience during the first four to eight weeks of resmetirom as hepatic metabolic remodeling occurs.

Community Programs, Senior Centers, and Structured Education

What "School" Means for Geriatric MASH Patients

The term "school" in the geriatric context refers to structured patient education programs, disease management classes, and community wellness curricula, not academic schooling. For MASH patients over 65, the most relevant programs include:

• Liver disease education programs offered through academic medical centers and patient advocacy groups such as the NASH Education Program
• Diabetes self-management education and support (DSMES) programs, which are directly relevant because 40 to 50% of MASH patients have concurrent type 2 diabetes [2]
• Cardiac rehabilitation programs, which include supervised exercise and dietary counseling applicable to MASH-associated dyslipidemia

The American Association for the Study of Liver Diseases (AASLD) 2023 Practice Guidance states: "Lifestyle intervention programs that combine dietary modification with physical activity remain the cornerstone of MASH management and should be offered to all patients regardless of pharmacotherapy status." [12]

Dietary Education in Structured Programs

Resmetirom does not impose specific dietary restrictions beyond what standard MASH management already requires, but the drug's interactions with grapefruit juice (a CYP3A4 inhibitor) mean that dietary counselors in senior programs should screen for habitual grapefruit consumption. [5] Protein intake of at least 1.2 g/kg/day is appropriate for older adults with MASH to protect lean mass while the liver undergoes fibrosis regression. [13]

A practical three-tier activity framework for geriatric patients on resmetirom, developed for HealthRX clinical guidance, categorizes patients by functional status:

• Tier 1 (strong, SPPB score 10-12): 150+ minutes/week moderate aerobic plus 2x/week resistance training; no activity modification needed beyond standard statin-myopathy surveillance
• Tier 2 (pre-frail, SPPB score 7-9): 75-150 minutes/week light-to-moderate aerobic (walking, cycling) plus Otago balance exercises 3x/week; CK check at baseline and 8 weeks if on concurrent statin
• Tier 3 (frail, SPPB score <7): chair-based exercises, supervised hydrotherapy, and physical therapy referral; hepatologist communication required before advancing activity intensity

Thyroid-Related Symptoms and Their Effect on Exercise Capacity

Resmetirom is selective for THR-beta, but off-target THR-alpha activity at higher exposures cannot be entirely excluded. In MAESTRO-NASH, hyperthyroid-like adverse events (palpitations, tremor, increased sweating) occurred in 4.2% of the resmetirom 100 mg group versus 2.1% placebo. [4] In older adults, even mild subclinical thyrotoxicosis reduces exercise tolerance and raises the risk of atrial fibrillation.

TSH should be checked at baseline, at 12 weeks, and then every six months in adults over 65 on resmetirom. [5] Any TSH below 0.5 mIU/L warrants dose reduction discussion with the prescribing hepatologist before continuing structured exercise programs above light intensity. [14]

Cardiac Monitoring Before Starting Exercise Programs

The American College of Cardiology and American Heart Association guidelines recommend that older adults with two or more cardiovascular risk factors (hypertension, dyslipidemia, diabetes, smoking history, family history) undergo a clinical cardiovascular assessment before beginning moderate-to-vigorous structured exercise. [7] MASH patients over 65 almost universally carry two or more of these risk factors. [2] A resting ECG and functional assessment (e.g., six-minute walk test) before enrolling in a senior exercise program is reasonable standard practice.

Drug Interactions Relevant to Activity Participation

Statins and Myopathy Risk During Exercise

Resmetirom inhibits OATP1B1 and OATP1B3 transporters, raising plasma concentrations of co-administered statins. [5] In a drug-drug interaction substudy, rosuvastatin AUC increased by approximately 2-fold when co-administered with resmetirom 100 mg. [5] Vigorous exercise independently increases CK and can precipitate myopathy in statin-treated patients. Older adults on rosuvastatin or atorvastatin who start a new moderate-to-vigorous exercise program while on resmetirom should have a baseline CK measured and a repeat check at four weeks if any muscle symptoms develop. [15]

Anticoagulants and Fall Risk

A substantial minority of adults over 65 with MASH-related cardiovascular comorbidities are on anticoagulants (warfarin or direct oral anticoagulants). Resmetirom does not have a documented pharmacokinetic interaction with warfarin in the prescribing information, but falls during exercise in anticoagulated patients carry elevated bleeding risk. [5] Activity programs for this subgroup should avoid contact sports and high-fall-risk exercises such as unassisted outdoor cycling on uneven terrain.

Common Geriatric Polypharmacy Conflicts

The following drugs frequently prescribed to adults over 65 require particular attention when resmetirom is added:

• Gemfibrozil: contraindicated (strong CYP2C8 inhibition raises resmetirom exposure 3.3-fold) [5]
• Cyclosporine: contraindicated (combined OATP inhibition and CYP inhibition) [5]
• Rifampin: avoid co-use (strong CYP2C8 inducer reduces resmetirom AUC by ~80%) [5]
• Fluconazole: use with caution (moderate CYP2C8 inhibition) [5]

Monitoring Schedule for Active Geriatric Patients on Resmetirom

Older adults who maintain an active lifestyle while on resmetirom need a monitoring schedule that integrates hepatic, thyroid, and musculoskeletal endpoints. The following schedule is consistent with the FDA label and the AASLD 2023 guidance: [5, 12]

At baseline: liver function tests (AST, ALT, bilirubin, ALP), fasting lipid panel, TSH, serum CK (if on statin), six-minute walk test or SPPB score, fall-risk assessment.

At 4 weeks: liver function tests, symptom review for muscle pain and palpitations.

At 12 weeks: liver function tests, fasting lipid panel, TSH, serum CK if symptomatic, activity tolerance reassessment.

At 26 and 52 weeks: full metabolic panel, fasting lipid panel, TSH, liver elastography or MRI-PDFF if available, SPPB score reassessment.

Liver Function Thresholds That Should Pause Exercise Escalation

ALT elevations greater than three times the upper limit of normal (ULN) on two consecutive measurements should prompt a temporary hold on vigorous exercise and immediate hepatologist review. [5] In MAESTRO-NASH, ALT elevation above 3x ULN occurred in 8.9% of the resmetirom 100 mg group. [4] Moderate activity (walking, light swimming) may continue during investigation if the patient is otherwise asymptomatic, but progression to high-intensity programs should wait until LFTs stabilize below 2x ULN.

Caregiver and Family Education in Geriatric Programs

Many adults over 65 with F2-F3 MASH rely on family members or professional caregivers for medication adherence and appointment navigation. Caregiver education should cover:

• Recognition of statin-myopathy symptoms (diffuse muscle aching, dark urine) and the importance of same-day CK testing
• Proper timing of resmetirom with or without food (the label states it can be taken without regard to meals) [5]
• Awareness that resmetirom does not cause hypoglycemia directly, but concurrent antidiabetic agents may require dose review as liver function improves, since insulin resistance decreases with MASH resolution [16]
• When to delay or skip a day's activity: fever above 38.5°C, resting heart rate above 100 bpm at wake-up, or new-onset bilateral leg edema

A 2023 systematic review in the Journal of Hepatology (N=14 studies, 2,847 patients) found that caregiver-assisted lifestyle interventions increased medication adherence in chronic liver disease patients over 60 by 22 percentage points compared with patient-alone interventions. [17]

Practical Prescribing Considerations for Clinicians Treating Active Older Adults

The REZDIFFRA prescribing information issued by Madrigal Pharmaceuticals specifies no upper age limit for use, and phase III data support efficacy across age subgroups. [5] The following practice points consolidate the evidence for clinicians:

1. Check SPPB or Timed Up-and-Go before initiating resmetirom in any patient over 65 to stratify activity risk at baseline.
2. Review the full statin prescription before prescribing; consider switching from rosuvastatin to pravastatin (which is not an OATP1B1 substrate) in patients planning vigorous exercise programs. [15]
3. Confirm gemfibrozil is not on the medication list. The drug-drug interaction is absolute, not dose-dependent. [5]
4. Schedule the 12-week TSH check as a standing order at the time of prescribing, before the patient leaves the clinic. Non-adherence to monitoring is higher in older adults with transportation barriers.
5. Document activity level in the chart at every visit using a validated scale such as the International Physical Activity Questionnaire (IPAQ) short form. Exercise is a free co-intervention that adds to resmetirom's liver-fat-reducing effects. [6]