Rezdiffra (Resmetirom) Real-World Evidence: What Registries and RWE Data Show Women

What Is Resmetirom and Why Does It Matter for Women?

Resmetirom (brand name Rezdiffra, made by Madrigal Pharmaceuticals) is a first-in-class, liver-directed thyroid hormone receptor beta (THR-beta) agonist taken as a once-daily oral tablet. The FDA approved it on March 14, 2024, making it the first drug specifically approved to treat MASH with moderate-to-advanced fibrosis. That matters for women because MASH is not a gender-neutral disease.

Women account for a disproportionate share of metabolic liver disease burden in specific hormonal contexts. MASH prevalence rises sharply in the perimenopausal transition and is closely linked to polycystic ovary syndrome (PCOS), insulin resistance, and visceral adiposity patterns that differ from men. Understanding where the real-world evidence (RWE) currently stands, and where it does not yet reach, is essential before you and your clinician decide whether resmetirom belongs in your care plan.

Why "Real-World Evidence" Is a Different Conversation Than a Clinical Trial

A phase 3 randomized controlled trial (RCT) like MAESTRO-NASH tells you what resmetirom can do under tightly controlled conditions. Real-world evidence, drawn from registries, electronic health records, insurance claims databases, and prospective observational cohorts, tells you what it actually does in the broader population of people who take it outside a trial, with their full complexity of comorbidities, polypharmacy, varied adherence, and life-stage variation.

For women, this distinction is especially consequential. RCTs routinely include fewer women, apply narrower eligibility criteria, and rarely analyze sex-disaggregated subgroups with enough statistical power to detect differences. Knowing which resmetirom findings come from trial data versus emerging RWE, and which are frankly extrapolated, lets you ask better questions at your next appointment.

The MAESTRO-NASH Trial: The Foundational Evidence Base

Before examining real-world data, you need a clear picture of the trial that established resmetirom's efficacy, because all current RWE is interpreted against this backdrop.

Trial Design and Population

MAESTRO-NASH was a phase 3, randomized, double-blind, placebo-controlled trial published in the New England Journal of Medicine in 2024. It enrolled 966 adults with biopsy-confirmed MASH and fibrosis stage F1B through F3. Participants were randomized 1:1:1 to resmetirom 80 mg, resmetirom 100 mg, or placebo once daily for 52 weeks.

The co-primary endpoints were:

1. NASH resolution (ballooning score of 0 and lobular inflammation score of 0 or 1) with no worsening of fibrosis
2. Fibrosis improvement of at least one stage with no worsening of NASH activity

Key Efficacy Numbers

At the 100 mg dose, 25.9% of participants achieved NASH resolution versus 9.7% on placebo (p <0.001). Fibrosis improvement by at least one stage occurred in 29.9% versus 19.9% on placebo (p <0.001). Both endpoints were met simultaneously in a meaningful subset, which is a higher bar than either endpoint alone.

LDL cholesterol fell by approximately 16% from baseline at 100 mg, and triglycerides fell by roughly 19%, consistent with resmetirom's mechanism of action on hepatic lipid metabolism.

Sex Composition of MAESTRO-NASH

Approximately 53% of MAESTRO-NASH participants were women, which is better representation than many metabolic-disease trials. However, sex-disaggregated efficacy and safety subgroup analyses have not been published as a primary or secondary report in a peer-reviewed journal as of this writing. The overall trial results therefore remain the best available evidence, with sex-specific conclusions being extrapolated rather than directly demonstrated. This is an honest and important gap.

Mechanism of Action: How Resmetirom Works in the Liver

Understanding the mechanism is not academic for women. THR-beta selectivity has direct relevance to your thyroid health, your lipid panel, and how hormonal status might modify the drug's effects.

THR-Beta Selectivity and Hepatic Lipid Metabolism

Thyroid hormone exerts its metabolic effects through two receptor subtypes: THR-alpha, which mediates heart rate, bone turnover, and central nervous system effects, and THR-beta, which predominantly drives hepatic lipid oxidation, cholesterol metabolism, and gluconeogenesis. Resmetirom was designed to be liver-directed and THR-beta selective, concentrating in hepatocytes while minimizing systemic THR-alpha stimulation that would cause tachycardia or bone loss.

In the liver, THR-beta activation increases mitochondrial fatty acid beta-oxidation, reduces de novo lipogenesis, upregulates LDL receptor expression, and promotes reverse cholesterol transport. The net result is reduced hepatic fat accumulation and less lipotoxicity-driven inflammation, which directly targets the pathophysiology driving MASH.

Why This Matters If You Have Thyroid Disease

Women have roughly five to eight times the rate of autoimmune thyroid disease compared with men. If you are on levothyroxine for hypothyroidism, resmetirom may alter thyroid hormone distribution or laboratory interpretation. The prescribing information flags a potential interaction with levothyroxine and recommends monitoring TSH in the first several months of treatment. This is a clinically specific point your prescriber should review with your endocrinologist if applicable.

The Lipid Connection to Female Metabolic Disease

Women's lipid profiles shift meaningfully across the menopausal transition: LDL rises, HDL tends to fall, and triglycerides increase. Resmetirom's reductions in LDL and triglycerides observed in MAESTRO-NASH are therefore potentially relevant beyond liver histology, particularly for perimenopausal women with metabolic syndrome. Whether these lipid benefits are durable beyond 52 weeks or differ by hormonal status is not yet established in RWE.

Real-World Evidence: What Exists Now and What Is Coming

This is where intellectual honesty is required. As of mid-2025, resmetirom has been commercially available for approximately 15 months. Formal registry-level RWE is nascent.

What "Real-World Evidence" Currently Exists

No large, peer-reviewed RWE publication specifically on resmetirom effectiveness in clinical practice has been indexed on PubMed as of this writing. What does exist includes:

• Single-center case series and early experience reports from academic liver centers, mostly presented at conferences such as The Liver Meeting (AASLD) but not yet peer-reviewed in full.
• TARGET-NASH registry: This longitudinal, U.S.-based real-world registry (TARGET-NASH) has been enrolling NASH/MASH patients since before resmetirom's approval and is now capturing patients initiating resmetirom in routine care. Published analyses with resmetirom-specific data are expected but have not appeared in indexed literature at this writing.
• Electronic health record (EHR) cohort analyses: Pharmacy claims and EHR-based cohorts from large health systems are being assembled. None have been peer-reviewed yet.
• Patient registries from Madrigal's MAESTRO-OUTCOMES trial: This ongoing outcomes trial is designed to assess cardiovascular and liver-related events over several years and will generate a large dataset, but it remains in the enrollment and follow-up phase.

The framework most clinicians are using for resmetirom in real-world practice right now is therefore a hybrid: the MAESTRO-NASH histological data provides the efficacy anchor; individual patient factors (thyroid status, PCOS, menopausal status, concurrent medications, fibrosis stage) inform dose and monitoring decisions; and emerging single-center experience is shared informally across hepatology networks while the formal registries mature.

What Early RWE Signals Are Emerging

Conference presentations from AASLD 2024 and preliminary reports from European hepatology centers suggest several early real-world observations, though none of these are peer-reviewed primary data:

1. Real-world patients tend to have more comorbidities than trial enrollees, including higher rates of type 2 diabetes (T2DM), cardiovascular disease, and concurrent GLP-1 receptor agonist use.
2. Adherence at 12 months appears lower in real-world settings than in trials, particularly among patients managing multiple daily medications.
3. The combination of resmetirom with GLP-1 receptor agonists (semaglutide, tirzepatide) is being used in clinical practice, despite no head-to-head or combination RCT data currently available.

For women, that third point is particularly relevant. GLP-1 receptor agonists are increasingly prescribed for PCOS, obesity, and metabolic syndrome, conditions that substantially overlap with the MASH population. The safety and effectiveness of this combination in women specifically has not been formally studied.

Women-Specific Conditions That Intersect with MASH and Resmetirom

MASH does not arrive in isolation for most women. Understanding the comorbidity field shapes how resmetirom fits into your broader care.

PCOS and Metabolic Liver Disease

PCOS affects approximately 8-13% of women of reproductive age and carries a markedly elevated risk of NAFLD/MASH driven by hyperinsulinemia, androgen excess, and visceral adiposity. Women with PCOS were not specifically analyzed as a subgroup in MAESTRO-NASH, and resmetirom has no current PCOS-specific indication. However, given the mechanistic overlap (hepatic insulin sensitization, lipid lowering, reduction of lipotoxicity), resmetirom is being used off-label consideration for PCOS women with biopsy-confirmed MASH who meet the approved indication criteria. This is extrapolated reasoning, not direct evidence.

Perimenopause and Postmenopause

The menopausal transition is an independent accelerant of metabolic liver disease. Estrogen loss after menopause is associated with increased hepatic fat accumulation and worsening insulin resistance, independent of body weight change. MASH prevalence in postmenopausal women may approach or exceed that in men of similar age, closing the sex gap that exists during reproductive years.

No subgroup analysis from MAESTRO-NASH specifically examines outcomes by menopausal status. In real-world practice, perimenopausal and postmenopausal women with MASH who are already on systemic menopausal hormone therapy (MHT) represent a population not captured in the trial, and how MHT interacts with resmetirom's THR-beta-mediated effects on lipid metabolism is genuinely unknown. Your hepatologist and gynecologist should coordinate if this describes your situation.

Type 2 Diabetes and Female Metabolic Syndrome

Approximately 50-60% of MAESTRO-NASH participants had T2DM. Women with T2DM have a different cardiovascular risk profile than men with T2DM, and they are often underrepresented in metabolic trials. Resmetirom's LDL and triglyceride lowering may be additive to statin or fibrate therapy, but drug interactions and liver enzyme monitoring schedules need to be individualized.

Female Pattern Hair Loss and Thyroid Considerations

Because resmetirom acts on thyroid hormone receptors, any woman with a history of thyroid disease or thyroid-related hair loss should have her TSH and free T4 checked at baseline and monitored during the first year. The Rezdiffra prescribing label specifically notes potential interaction with levothyroxine, recommending dose adjustment monitoring.

Pregnancy, Lactation, and Contraception: A Required Section

Resmetirom is contraindicated in pregnancy. This is not a relative caution. It is an absolute contraindication based on animal reproductive toxicity data, and women of reproductive potential must use reliable contraception during treatment.

Pregnancy Safety Data

Animal studies with resmetirom demonstrated embryo-fetal toxicity at doses relevant to human exposure. No adequate human pregnancy data exist. Because MASH affects a broad age range including women of reproductive age with PCOS or metabolic syndrome, this contraindication has practical clinical weight. Resmetirom should be discontinued immediately if pregnancy is confirmed, and the patient should contact her obstetric provider.

The FDA has not assigned a traditional letter pregnancy category since those were phased out in 2015, but the Pregnancy and Lactation Labeling Rule (PLLR) section of the Rezdiffra label is explicit: animal data show harm, human data are absent, and the drug should not be used during pregnancy.

Contraception Requirements

Women of reproductive age who are prescribed resmetirom should be using a highly effective contraceptive method. This includes hormonal contraceptives (pill, patch, ring, injection, implant, hormonal IUD), copper IUD, or a combination of barrier methods, depending on individual preference and comorbidities. Your prescriber and gynecologist should align on contraceptive planning before starting resmetirom.

Given that resmetirom may be co-prescribed with medications such as statins or fibrates that also carry pregnancy warnings, the contraceptive conversation is not optional and should be documented at the time of prescription.

Lactation

It is unknown whether resmetirom or its metabolites are present in human breast milk. Given the theoretical potential for harm to a nursing infant and the absence of data, the prescribing information advises against breastfeeding during treatment. Women who are postpartum and breastfeeding should discuss the timing of any initiation of resmetirom with their hepatologist and their infant's pediatrician.

Trying to Conceive

For women with PCOS or other conditions who are simultaneously managing MASH and working toward conception, resmetirom is not compatible with active conception attempts. The drug must be discontinued with adequate washout time before attempting pregnancy, and the prescribing label should be reviewed for current guidance on washout duration. Fertility specialists and hepatologists should coordinate care in this situation.

Who This Drug Is and Is Not Right For (By Life Stage)

Reproductive-Age Women (18-40)

Resmetirom may be appropriate if you have biopsy-confirmed MASH with F2 or F3 fibrosis, are not pregnant or breastfeeding, and are using reliable contraception. Women with PCOS in this age group who meet these criteria are potential candidates, though the PCOS-specific evidence base is extrapolated rather than trial-proven. Liver biopsy remains the gold standard for patient selection; non-invasive biomarkers (FIB-4, liver stiffness measurement) are being studied as alternatives in real-world practice but are not currently validated for treatment decision-making in the label.

Perimenopausal Women (40-55)

This group may have the highest unmet need. Estrogen decline accelerates hepatic fat accumulation and metabolic dysfunction, and many perimenopausal women carry MASH that has progressed silently. If you are in perimenopause and have elevated liver enzymes, metabolic syndrome, or a history of PCOS, liver disease screening with FIB-4 and, where indicated, biopsy is reasonable. Resmetirom is not contraindicated in perimenopause, and contraception remains necessary until menopause is confirmed (12 consecutive months of amenorrhea in the appropriate clinical context).

Postmenopausal Women

The contraindication argument around pregnancy does not apply, but monitoring for thyroid effects, bone density, and drug interactions with any MHT, antilipid agents, or diabetes medications is clinically important. This is a group where resmetirom's lipid-lowering secondary effects may be especially meaningful alongside its primary hepatic benefit.

Women with Cirrhosis (F4)

Resmetirom is not approved for compensated or decompensated cirrhosis. MAESTRO-NASH enrolled only F1B through F3. Using it in cirrhosis is off-label, and early signals from case reports suggest the hepatic pharmacokinetics may differ in this population. Real-world RWE in cirrhosis is a critical gap.

Safety Profile and Monitoring in Clinical Practice

Common Adverse Effects in MAESTRO-NASH

The most common adverse effects in the trial were gastrointestinal: nausea occurred in approximately 26% at 100 mg versus 11% placebo, and diarrhea in about 28% versus 15%. Most GI symptoms were mild to moderate and occurred within the first 8 weeks.

Dose-related increases in ALT and AST occurred transiently in a subset of patients. Gallstones and biliary events were observed at slightly higher rates than placebo, consistent with the drug's effect on bile acid metabolism.

Women with a history of gallbladder disease, prior cholecystectomy, or rapid weight loss on concurrent GLP-1 therapy should discuss the additive biliary risk with their provider.

Thyroid Monitoring

TSH should be checked at baseline. The prescribing label recommends monitoring TSH after 3 months and then periodically in patients on levothyroxine, as resmetirom may reduce the dose of levothyroxine needed. Women already diagnosed with Hashimoto thyroiditis or Graves disease should have their thyroid clinician involved from the start.

Liver Enzyme Monitoring

ALT and AST should be checked before starting, at 3 months, and then per your hepatologist's standard schedule. A 3-fold or greater rise above the upper limit of normal that persists, or any clinical signs of hepatotoxicity, warrants prompt evaluation and potential discontinuation.

The Evidence Gap: What We Still Do Not Know About Women and Resmetirom

Being honest about gaps is more useful to you than projecting false certainty.

1. No published sex-disaggregated subgroup analysis from MAESTRO-NASH. The trial enrolled slightly more women than men, but the data have not been analyzed and published by sex.
2. No RWE on resmetirom in women with PCOS as a defined cohort.
3. No data on resmetirom combined with systemic menopausal hormone therapy.
4. No pregnancy exposure data in humans. Animal data are harmful; human exposures in the post-marketing period will be tracked via the Madrigal pregnancy registry, but data are not yet reported.
5. No long-term (beyond 52 weeks) histological outcome data from any source, trial or real-world.
6. No comparative effectiveness data against GLP-1 receptor agonists in women with MASH and obesity or PCOS.

The TARGET-NASH registry and MAESTRO-OUTCOMES trial will address several of these gaps over the next 3-5 years. Until then, clinical decisions for women rely on the MAESTRO-NASH overall results, mechanism-informed reasoning, and individualized risk-benefit conversations.

Practical Steps If You Are Considering Resmetirom

Your liver specialist will need a current liver biopsy confirming MASH with F2 or F3 fibrosis to justify prescribing. Non-invasive testing alone does not meet the approved indication criteria at this time. Before your appointment, it helps to compile:

• All current medications, including thyroid medications, statins, GLP-1 agonists, oral contraceptives, and any supplements
• Recent thyroid function tests (TSH, free T4)
• Recent lipid panel and metabolic panel
• Reproductive history and current contraceptive method
• History of gallbladder disease or gallstones

A baseline liver ultrasound and TSH, plus a clear contraceptive plan, are minimum pre-initiation steps. At 100 mg, the monthly cost without insurance is substantial (approximately $47,400 per year list price per some early payer analyses), and prior authorization requirements vary significantly by insurer. Your hepatology team's pharmacy navigator or a Madrigal patient support program may be the most direct path to access.