Dr. Jonathan Leffert

Dr. Jonathan Leffert Jonathan Leffert, MD is a board certified endocrinologist.

He offers thyroid RFA, a nonsurgical and thyroid sparing treatment option for patients with thyroid nodules.

02/21/2026

The 15% Difference: Why Your Generic Thyroid Meds Might Be Fluctuating 📉💊

Did you know the FDA allows a "leeway" in the potency of your thyroid medication?

In this clip, Dr. Jonathan Leffert breaks down a critical detail: a 100mcg dose of generic Levothyroxine from "Manufacturer A" can be up to 15% different in potency compared to "Manufacturer B" or a brand-name like Synthroid.

For a medication with a Narrow Therapeutic Index, that small percentage can be the difference between feeling great and falling back into brain fog or fatigue.

What you need to know:

👉The Pharmacy Factor: Pharmacies often switch generic manufacturers based on stock. You might be getting a different "version" of your dose without even knowing it.

👉Consistency is Key: It’s not that generics are "bad"—it’s that switching causes the issue. If you use a generic, try to stay with the same manufacturer every month.

👉The 6–8 Week Rule: If you do switch from brand-name to generic (or between different generics), make sure you get retested in 6 to 8 weeks to ensure your levels are still stable.

Don't let a manufacturing switch disrupt your health trajectory. Stay consistent, stay informed, and always advocate for your labs.

📍 Expert Endocrine Care | Dallas, TX
🔗 Learn more about optimizing your thyroid: ntendocenter.com/rfa

02/20/2026

Brand Name vs. Generic: Does it really matter for your thyroid? 🤔💊

If your thyroid labs are constantly jumping from the "green zone" to the "red zone," the culprit might be your pharmacy bag, not your body.

In this clip, Dr. Jonathan Leffert explains the Narrow Therapeutic Index—the tiny window between a dose that works and a dose that doesn't. When it comes to thyroid hormone, small differences in manufacturing can lead to big changes in how you feel.

Why Consistency is King:

😎The "Brand" Advantage: Branded T4 medications like Synthroid or Unithroid come from a single manufacturer, ensuring the potency is consistent every single month.

😎The Generic Gamble: Generic T4 Levothyroxine can come from various manufacturers. If your pharmacy changes their supplier, your "100mcg" dose might actually feel slightly different to your body.

😎Staying in the Green: To keep your levels stable, consistency in the medication itself is just as important as taking it at the same time every day.

Watch to find out why Dr. Leffert emphasizes staying with one consistent T4 source to keep your thyroid health on the right trajectory.

📍 Dr. Jonathan Leffert | Dallas, TX
🔗 Optimize your thyroid journey: ntendocenter.com/rfa

02/19/2026

Are you getting the "Full Value" of your thyroid medication? 💊🤔

It’s not just about the dosage your doctor prescribes—it’s about how much of that dose your body actually absorbs. In this clip, Dr. Jonathan Leffert explains why "purity of the stomach" is the secret to successful thyroid hormone replacement.

The Absorption Blockers:
❌ Food: Eating too soon can prevent your pill from working effectively.
❌ Calcium & Iron: These common vitamins are notorious for binding to thyroid hormone.
❌ Acid Reflux Meds: PPIs like Prilosec (Omeprazole) can significantly inhibit absorption.

The Golden Rule:
Take your medication by itself, ideally first thing in the morning (or even the middle of the night!), and wait 30 to 60 minutes before eating or taking other medications.

Consistency is the key to moving your labs into the "green zone" and finally feeling like yourself again.

📍 Expert Thyroid Care in Dallas, TX
🔗 See if you’re a candidate for our advanced treatments: ntendocenter.com/rfa

There is no greater honor in medicine than walking alongside a patient for nearly 30 years. 💙We are so moved by this rec...
02/17/2026

There is no greater honor in medicine than walking alongside a patient for nearly 30 years. 💙

We are so moved by this recent review from a long-time patient who first came to Dr. Leffert with a goiter that led to a follicular thyroid cancer diagnosis. From diagnosis through surgery and decades of survivorship, Dr. Leffert has been there every step of the way.

"I’ve been a patient of Dr. Leffert’s for almost 30 years. He started treating me when I had a huge thyroid goiter, which later was diagnosed as follicular thyroid cancer and surgically removed. Dr. Leffert, has guided me throughout my thyroid journey and I wouldn’t see anyone else. His knowledge is impeccable and his compassion remarkable. The office is always professional and courteous, with exceptional response turn around. I’m indebted to Dr. Leffert, and would recommend him 10x over." - Tamitha P.

Our mission has always been to combine "impeccable knowledge" with "remarkable compassion," and we are so grateful for the trust our patients place in us for their lifelong thyroid journeys.

Thank you for the kind words and for being part of our practice family!

Are you looking for an experienced endocrinologist in the Dallas area?
Contact our office today!
North Texas Endocrine Center 🌐 ntendocenter.com 📞 (214) 369-5992

02/13/2026

Do you really need to fast for your thyroid blood test? 🧪🥨

Timing your lab work can be confusing, especially when you're balancing your morning medication. Dr. Jonathan Leffert explains why the type of medication you take changes the rules for your blood draw:

💊 Taking T4 (Levothyroxine/Synthroid): Since T4 is a long-acting hormone, your levels stay relatively stable. Fasting or specific timing usually isn’t critical for these tests.
💊 Taking T3 or Desiccated Thyroid (Armor/NP Thyroid/Cytomel): Because T3 is short-acting, timing matters much more. To get an accurate reading of your peak levels, it is often best to wait at least two hours after your dose before getting your blood drawn.

The best rule of thumb? Always check with your specialist to see how they want you to time your labs based on your specific protocol.

Looking for expert guidance on managing your thyroid hormone replacement? Contact the North Texas Endocrine Center.

📍 Location: 9301 N. Central Expressway, Suite 570, Dallas, TX 75231 📞 Call: (214) 369-5992 🌐 Website: https://www.ntendocenter.com/rfa

02/12/2026

Is your thyroid dose "just right," or is it time for a change? ⚖️🦋

Adjusting thyroid medication isn't just about chasing a number on a lab report; it’s about finding the clinical "sweet spot" where you feel great and stay healthy.

Dr. Jonathan Leffert explains the risks of having too much—or too little—thyroid hormone:

⚠️ Too Much (Over-replacement): Levels that are too high can lead to serious long-term complications, including heart rhythm disturbances (like AFib) and an increased risk for osteoporosis. 📉 Too Little (Under-replacement): If your dose is too low, you may struggle with persistent fatigue, weight gain, constipation, and dry skin.

Clinical care is a partnership. We use lab results and your reported symptoms together to determine if an adjustment is necessary to protect your long-term health while helping you feel your best today.
Schedule a Consultation

Get a specialized, safe approach to your thyroid hormone management at the North Texas Endocrine Center.

📍 Location: 9301 N. Central Expressway, Suite 570, Dallas, TX 75231 📞 Call: (214) 369-5992 🌐 Website: https://www.ntendocenter.com/rfa

02/12/2026

Why do your thyroid labs keep changing? 📊🤔

It’s frustrating to see your numbers fluctuate, but those variations aren't always a sign that your thyroid is failing.

Dr. Jonathan Leffert explains the hidden variables that can "skew" your thyroid test results:

🔬 Laboratory Assays: Different labs use different testing methods (assays). A result at one lab might look slightly different than a result at another.
💊 Medication Interference: Other medications you are taking can change how your thyroid hormones are measured or absorbed.
⚠️ The Biotin Factor: This common B-vitamin (found in hair and nail supplements) is a major culprit—it can actually interfere with the lab's equipment and give a false reading.

Whether you are currently on thyroid hormone replacement or just being monitored, understanding these variables is crucial to getting an accurate diagnosis.
Schedule a Consultation

Ensure your thyroid labs are being interpreted with expert clinical oversight. Contact the North Texas Endocrine Center.

📍 Location: 9301 N. Central Expressway, Suite 570, Dallas, TX 75231 📞 Call: (214) 369-5992 🌐 Website: https://www.ntendocenter.com/rfa

02/11/2026

Are your labs telling the whole story? 🩸🤔

When treating hypothyroidism, we use "Thyroid Function Tests" as our roadmap. But a great treatment plan is about more than just hitting a number on a page.

Dr. Jonathan Leffert explains how we monitor your progress:

🔹 The Roadmap: We use routine blood tests to see if your current dosage is adequate, or if we need to increase, decrease, or maintain your medication.
🔹 The "Missing" Piece: While the labs guide us, your symptoms are just as important. Clinical care is a coordination between what the data says and how you actually feel.
🔹 The Goal: Finding that "steady state" where your hormone levels are stable and your symptoms—like fatigue or brain fog—are addressed.

If you’re on thyroid hormone replacement, regular monitoring is the key to ensuring your dose is working for you, not against you.
Schedule a Consultation

Looking for a specialized approach to your thyroid treatment? Contact the North Texas Endocrine Center.

📍 Location: 9301 N. Central Expressway, Suite 570, Dallas, TX 75231 📞 Call: (214) 369-5992 🌐 Website: https://www.ntendocenter.com/rfa

02/10/2026

Fatigue? Weight gain? Dry skin? 🔍

If you’ve mentioned these symptoms to your primary care doctor, chances are they’ve ordered a "Thyroid Panel." But what exactly are those tests looking for?

Dr. Jonathan Leffert breaks down the standard clinical path for diagnosing Hypothyroidism:

1️⃣ The TSH Screening: This is the first line of defense. A high TSH actually signals that your thyroid is underactive (Hypothyroidism).
2️⃣ The Free T4: If your TSH is abnormal, we look at the Free T4 to see exactly how much hormone is circulating in your system.
3️⃣ The Antibody Test (TPO): Since Hashimoto’s thyroiditis is the #1 cause of low thyroid in the US, we test for thyroid peroxidase antibodies to confirm if an autoimmune response is the root cause.

While your primary care doctor often starts this process, an endocrinologist provides the specialized evaluation and long-term treatment strategy needed to get your levels—and your energy—back on track.
Schedule a Consultation

Get a comprehensive evaluation of your thyroid health at the North Texas Endocrine Center.

📍 Location: 9301 N. Central Expressway, Suite 570, Dallas, TX 75231
📞 Call: (214) 369-5992
🌐 Website: https://www.ntendocenter.com/rfa

"My labs are normal, so why do I still feel like this?" 🩺🤔It is one of the most frustrating experiences for a thyroid pa...
02/07/2026

"My labs are normal, so why do I still feel like this?" 🩺🤔

It is one of the most frustrating experiences for a thyroid patient: being told your levels are "in range" while you are still struggling with fatigue, brain fog, or other symptoms.

In this clip, Dr. Jonathan Leffert explains why "normal" isn't the same as "optimal." At the North Texas Endocrine Center, we don't just treat a piece of paper—we treat the person.

The Comprehensive Approach:

🤓Listen to the Symptoms: Your physical experience is a vital piece of the diagnostic puzzle.

📈Context Matters: We compare your current labs to your personal history and previous health data.

😎Individualized Care: Finding the "correct dosage" means looking at the whole picture, not just a lab range.

Don’t ignore what your body is telling you. If your labs are in range but your symptoms persist, it’s time for a deeper conversation.

Ready for a provider who looks beyond the basic lab range? Let's discuss your thyroid health trajectory and non-surgical options like RFA.

🔗 Connect with our clinic: ntendocenter.com/rfa

🤓

02/06/2026

STOP taking your Biotin before your thyroid labs! 🛑💊

Are your thyroid results actually accurate? If you’re taking a hair, skin, and nail supplement, you might be getting a false reading.

In this quick tip, Dr. Jonathan Leffert explains why Biotin supplements (Vitamin B7) can interfere with the laboratory assays used to measure your T4 and TSH levels. This interference can make your labs look hyperthyroid or hypothyroid even when they aren’t—potentially leading to a change in your prescription that you don't actually need.

The Rule of Thumb: Stop all Biotin-containing supplements 3 to 5 days before you head to the lab for your thyroid blood work.

Don't let a simple vitamin interfere with your thyroid management!

Expert Thyroid Care in Dallas, TX! If you have questions about your thyroid labs or are looking for non-surgical options for thyroid nodules, we are here to help.

🔗 Visit us to learn more: ntendocenter.com/rfa

02/04/2026

Many patients believe that the only way to deal with a large, symptomatic thyroid nodule is to remove half—or all—of the thyroid gland. But why sacrifice a healthy, functioning organ if you don't have to?

In this video, Dr. Jonathan Leffert explains the RFA difference: a 30-minute, non-surgical solution that targets the nodule while leaving your thyroid gland intact.

📘 The Full Breakdown: How Thyroid RFA Works

1. The Consultation & Mapping Before the procedure, we use high-resolution ultrasound to "map" the nodule, ensuring it is a benign candidate for ablation and identifying nearby structures like the vocal cord nerves to ensure maximum safety.

2. Local Numbing (No General Anesthesia) Unlike traditional surgery, RFA does NOT require you to be "put under." We use local numbing and a technique called lidocaine hydro-dissection. This creates a protective fluid barrier around the thyroid, making the procedure virtually painless while allowing you to remain awake and talk to the medical team.

3. The Ablation Process A specialized, thin probe is inserted into the nodule under constant ultrasound guidance. Using thermal energy (radiofrequency), we treat the nodule tissue from the inside out. The procedure typically takes only 30–40 minutes.

4. The Recovery Because there is no incision, there is no surgical scar. You walk out of the office with a small band-aid. Most patients return to work and normal activities the very next day.

5. The Results Over the following months, your body naturally reabsorbs the treated tissue, causing the nodule to shrink significantly. This relieves symptoms like difficulty swallowing or neck pressure—all while preserving your natural thyroid function.
Ready to see if you're a candidate?

Consult with Dr. Leffert at the North Texas Endocrine Center to discuss saving your thyroid.

📍 Location: 9301 N. Central Expressway, Suite 570, Dallas, TX 75231
📞 Call: (214) 369-5992 🌐 ntendocenter.com/rfa

Address

NORTH TEXAS ENDOCRINE CENTER: Carrell Clinic Center, Tower II, 9301 North Central Expressway, Suite 570
Dallas, TX
75231

Opening Hours

Monday 8am - 4:30pm
Tuesday 8am - 4:30pm
Wednesday 8am - 4:30pm
Thursday 8am - 4:30pm
Friday 8am - 4:30pm

Telephone

+12143695992

Website

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