Thyroid Conditions

Unexplained Weight Changes

Gaining weight for no clear reason—or struggling to lose it despite diet and exercise—can signal an underactive thyroid slowing your metabolism and energy balance.

Mood Swings & Brain Fog

When thyroid hormones fall out of balance, they affect the brain too—bringing brain fog, trouble concentrating, memory lapses, irritability, and mood swings that feel hard to explain.

Managing Thyroid With
Confidence

Constant Fatigue and Low Energy

Persistent tiredness, weakness, and low stamina—even after a full night’s rest—can be a sign your thyroid isn’t producing enough energy-regulating hormone to keep you going through the day.

Symptoms That Keep Coming Back

If your symptoms fade and return—or never fully resolve even with treatment—it may mean your thyroid levels need closer monitoring and a more personalized, endocrinology-led plan.

Comprehensive Thyroid Care for Lasting Health

At EndoInnova, board-certified endocrinologist Dr. Sheila S. Mercado Méndez delivers personalized thyroid care built on accurate diagnosis and effective treatment. From hypothyroidism treatment to hyperthyroidism, Hashimoto’s, and thyroid nodule care, her comprehensive evaluations, evidence-based therapies, and ongoing monitoring help restore hormonal balance and support your long-term health across Puerto Rico.

Thyroid Disorder Management

Endocrinology-led diagnosis and management of thyroid disorders—each plan built around your hormone levels, symptoms, and goals, with regular follow-up to keep your thyroid function on track.

Advanced Muscle Mass and Body Composition Testing

EndoInnova will soon offer InBody 580 body composition testing as part of our endocrinology-led evaluations. This advanced analysis goes beyond the scale—measuring muscle mass, body fat, visceral fat, and water balance—to give Dr. Sheila S. Mercado Méndez a clearer picture of your metabolic and thyroid health across Puerto Rico.

Advanced Measurement System

The InBody 580 delivers precise, segmental body composition data for detailed, reliable health analysis.

Easy to Use

A simple, intuitive design makes each measurement quick, comfortable, and accurate—no complicated setup.

Fast Assessment

A full body composition analysis takes about 30 seconds, with clear results ready for quick review.

Smart Connectivity

A QR-based system enables easy data entry and smooth digital integration into your care record.

Your Thyroid Journey Made Simple

A clear, step-by-step path—guided by Dr. Sheila S. Mercado Méndez—to diagnosing your thyroid, balancing your hormones, and protecting your long-term health.

01

Identify Thyroid Symptoms

We start with a detailed review of your energy, metabolism, weight changes, and medical history to build a complete picture of how your thyroid is functioning.

02

Precision Hormone Assessment

Advanced lab work and clinical evaluation help pinpoint hormonal imbalances—TSH, Free T4, Free T3, and antibodies—to identify the root cause of your symptoms.

03

Personalized Treatment Plan

Dr. Mercado tailors a plan combining medication, lifestyle adjustments, and nutrition to restore hormonal balance and improve your overall metabolic health.

04

Monitor & Optimize

Regular follow-ups let us fine-tune your treatment, track hormone levels over time, and support your long-term vitality and stability.

Your Personalized Endocrine Care Program

A comprehensive, endocrinology-led program guided by board-certified endocrinologist Dr. Sheila S. Mercado Méndez—focused on accurate diagnosis, hormone balance, and long-term management of hypothyroidism, hyperthyroidism, Hashimoto’s, and thyroid nodules through personalized care and ongoing monitoring in Puerto Rico.

Personalized Thyroid Care With a Clear Purpose

Specialized, endocrinology-led thyroid care, patient education, and comprehensive diagnostic testing with Dr. Sheila S. Mercado Méndez—designed to make your health decisions clearer and easier across Puerto Rico.

200+

Recovered patients

95%

Recovery Rate

24*7

Support System

Care plans built around your specific thyroid diagnosis, hormone levels, lifestyle, and long-term wellness goals.

Endocrinology-led support for hypothyroidism, hyperthyroidism, thyroid nodules, and complex autoimmune thyroid conditions like Hashimoto’s.

Hormonal testing and diagnostic studies, as appropriate for each case, to assess thyroid function and guide a personalized treatment plan.

Patient Stories That Inspire Confidence

Real experiences from patients who value clear guidance, compassionate care, and a better understanding of their health.

Frequently Asked
Questions

Answers to common questions about thyroid symptoms, diagnosis, and treatment—so you can make clearer decisions about your thyroid health with a trusted endocrinologist for thyroid in Puerto Rico.

What are the common symptoms of thyroid disorders?

Common thyroid symptoms include fatigue, unexplained weight changes, hair loss, brain fog, mood changes, and sensitivity to heat or cold. Because these overlap with many other conditions, an evaluation with a thyroid doctor in Puerto Rico is the most reliable way to confirm whether your thyroid is the cause.

Thyroid disorders develop gradually, so symptoms are often dismissed as stress, aging, or a busy lifestyle before anyone considers the thyroid. An underactive thyroid (hypothyroidism) tends to slow the body down — bringing persistent tiredness, weight gain, constipation, dry skin, cold intolerance, and low mood. An overactive thyroid (hyperthyroidism) does the opposite, causing weight loss, a racing or irregular heartbeat, anxiety, tremors, heat intolerance, and trouble sleeping. Autoimmune conditions such as Hashimoto’s can produce a fluctuating mix of both patterns over time.

Many patients come to EndoInnova after months of searching for a doctor for unexplained fatigue and weight gain in Puerto Rico, having been told their results were “normal.” That’s exactly why a specialist evaluation matters: board-certified endocrinologist Dr. Sheila S. Mercado Méndez reviews your full symptom picture — energy, metabolism, weight, mood, and cardiovascular changes — alongside your medical and family history, not just a single lab value.

Symptoms alone can’t confirm a diagnosis, but they signal when testing is warranted. If several of these signs persist for weeks, or if thyroid disease runs in your family, an endocrinology-led assessment is the right next step. Dr. Mercado combines your symptoms with targeted hormone testing to identify whether your thyroid is underactive, overactive, or affected by an autoimmune process — then builds a personalized plan to help you feel like yourself again. Book an evaluation with EndoInnova in Hatillo to get clear answers.

Why is my TSH normal but I still have thyroid symptoms?

A normal TSH doesn’t always mean your thyroid is fully healthy. Symptoms can persist because of antibody activity, Free T4 or Free T3 imbalances, or medication that isn’t optimized. An endocrinologist for thyroid in Puerto Rico can look beyond a single number to find what’s really going on.

TSH is a useful screening test, but it’s only one piece of the picture. It measures the signal your pituitary sends to the thyroid — not the actual thyroid hormones circulating in your body. Someone can have a TSH within the “normal” reference range and still feel unwell if their Free T4 or Free T3 sits at the low end, if their levels swing due to Hashimoto’s, or if the standard range simply isn’t optimal for them.

This is one of the most common frustrations patients bring to EndoInnova. If you’ve wondered why your TSH is normal but you still have symptoms, you’re not imagining it. Board-certified endocrinologist Dr. Sheila S. Mercado Méndez orders a fuller panel when the clinical picture calls for it — TSH, Free T4, Free T3, and thyroid antibodies (TPO and thyroglobulin) — and interprets those results together with your symptoms rather than in isolation.

Antibodies matter especially here: in early Hashimoto’s thyroiditis, antibodies can be elevated and symptoms present years before TSH moves out of range. For patients already on treatment, persistent symptoms may mean the dose, timing, or formulation needs adjusting. Dr. Mercado also checks for overlapping causes — iron, vitamin D, or other issues that mimic thyroid symptoms.

The goal is context, not a single lab flag. If your labs read “normal” but you still don’t feel right, an endocrinology-led re-evaluation in Puerto Rico can uncover the cause and guide a plan that actually addresses how you feel.

What kind of doctor treats thyroid nodules?

An endocrinologist is the specialist who evaluates and treats thyroid nodules. At EndoInnova in Puerto Rico, board-certified endocrinologist Dr. Sheila S. Mercado Méndez assesses nodules using clinical examination, thyroid hormone testing, and ultrasound when needed, then guides monitoring or treatment based on your individual results.

Thyroid nodules are common — many are found by chance during a physical exam or an unrelated scan — and the great majority are benign. Still, because a small percentage can be concerning, they deserve proper evaluation by a thyroid nodule doctor in Puerto Rico rather than a wait-and-see approach at home. An endocrinologist is specifically trained to tell which nodules simply need periodic monitoring and which warrant further study.

When you see Dr. Mercado about a nodule, the assessment typically starts with your history and a physical exam, followed by blood tests to check whether the nodule is affecting your thyroid hormone levels. Thyroid ultrasound helps characterize a nodule’s size, structure, and features. Depending on those findings, she may recommend continued monitoring over time or additional evaluation such as a fine-needle aspiration biopsy, coordinated with the appropriate specialists.

Most nodules never cause problems and only need periodic follow-up to confirm they remain stable. Others — particularly those affecting hormone production or showing certain ultrasound features — benefit from a clear, individualized plan. Autoimmune conditions like Hashimoto’s can also be associated with nodular changes, which is why an endocrinology-led evaluation looks at the whole thyroid, not just one spot.

If you’ve felt a lump in your neck, had a nodule mentioned on imaging, or been searching for what kind of doctor treats thyroid nodules, EndoInnova provides specialist evaluation and follow-up. Book an appointment with Dr. Mercado in Hatillo for a thorough, reassuring assessment.

Where can I find a Hashimoto's thyroiditis doctor near me?

If you’re looking for a Hashimoto’s thyroiditis doctor near you in Puerto Rico, EndoInnova provides specialized care for autoimmune thyroid disease. Board-certified endocrinologist Dr. Sheila S. Mercado Méndez offers antibody testing, hormone evaluation, and personalized management for patients across the North Coast and the San Juan metro area.

Hashimoto’s thyroiditis is the most common cause of hypothyroidism. It’s an autoimmune condition in which the immune system gradually attacks the thyroid, so hormone levels can drift slowly and symptoms — fatigue, weight gain, brain fog, cold intolerance, hair thinning — often appear before standard tests look clearly abnormal. That slow, fluctuating course is exactly why a Hashimoto’s specialist in Puerto Rico is valuable: the condition needs someone who tracks the trend, not just a one-time result.

As an endocrinologist, Dr. Mercado confirms Hashimoto’s using thyroid antibody testing (TPO and thyroglobulin antibodies) alongside TSH, Free T4, and Free T3, and correlates those numbers with how you actually feel. Because Hashimoto’s is lifelong, care is about steady, well-monitored management rather than a quick fix — the right medication when it’s needed, dose adjustments over time, attention to symptoms, and periodic re-testing to keep your levels where they should be.

Many patients with Hashimoto’s have spent years feeling dismissed. At EndoInnova, the focus is on listening, testing thoroughly, and explaining what’s happening in clear terms — in English or Spanish.

EndoInnova is based in Hatillo and cares for Hashimoto’s patients throughout Manatí, Arecibo, Camuy, Quebradillas, Barceloneta, Bayamón, and San Juan. If you’ve been searching for a Hashimoto’s thyroiditis doctor near me, book an appointment with Dr. Mercado for autoimmune thyroid care built around your long-term health.

What does hypothyroidism and hyperthyroidism treatment involve?

Hypothyroidism treatment in Puerto Rico usually involves thyroid hormone replacement and regular monitoring, while hyperthyroidism care may include medication and specialist coordination. Board-certified endocrinologist Dr. Sheila S. Mercado Méndez tailors treatment to your labs, symptoms, and health goals rather than a one-size-fits-all approach.

Treatment depends entirely on which direction your thyroid is off. In hypothyroidism (an underactive thyroid, often from Hashimoto’s), the thyroid doesn’t make enough hormone, so treatment typically replaces what’s missing and restores normal levels. The right dose is individual and can change over time, which is why follow-up testing matters — too little leaves symptoms in place, while too much causes its own problems. Dr. Mercado adjusts carefully based on your labs and how you feel, not a single reading.

Hyperthyroidism (an overactive thyroid) is managed differently. As a hyperthyroidism doctor in Puerto Rico, Dr. Mercado evaluates the underlying cause — such as Graves’ disease or an overactive nodule — and discusses the appropriate options, which may include medication to calm hormone production and coordination with other specialists when a case calls for it. Careful monitoring is essential because thyroid levels can shift as treatment takes effect.

For both conditions, treatment is about long-term balance rather than a cure. Most patients feel significantly better once their levels stabilize, but thyroid conditions are generally managed over time with periodic testing and adjustments. Lifestyle, nutrition, and consistent follow-up all support the medical side of the plan.

What ties it together is personalized, endocrinology-led care. Dr. Mercado explains your diagnosis clearly, sets realistic expectations, and builds a plan around your specific results — so you understand not just what you’re taking, but why. Book an evaluation at EndoInnova in Hatillo to start a thyroid treatment plan built for you.

Which areas does EndoInnova's thyroid clinic serve?

EndoInnova is a thyroid specialist clinic in Hatillo, Puerto Rico, serving patients across the North Coast and San Juan metro. Board-certified endocrinologist Dr. Sheila S. Mercado Méndez cares for thyroid patients from Manatí, Arecibo, Bayamón, San Juan, and surrounding towns.

Access to endocrinology-led thyroid care shouldn’t depend on where you live. While EndoInnova’s office is in Hatillo, patients travel from across the region because specialized thyroid care isn’t available in every town. If you’ve searched for a thyroid specialist in Hatillo, a thyroid doctor in Manatí, a thyroid specialist in Arecibo, a thyroid doctor in Bayamón, or a thyroid specialist in San Juan, EndoInnova serves your area.

Along Puerto Rico’s North Coast, the clinic regularly cares for patients from Manatí, Arecibo, Camuy, Quebradillas, and Barceloneta — communities within convenient reach of the Hatillo office. For patients in the metro area, Dr. Mercado also sees people traveling from Bayamón, San Juan, and nearby municipalities who want endocrinology-led evaluation for hypothyroidism, hyperthyroidism, Hashimoto’s, and thyroid nodules.

Every patient receives the same standard of care regardless of where they’re coming from: a thorough evaluation, appropriate thyroid testing, and a personalized plan explained clearly in English or Spanish. Bilingual care means you and your family fully understand your diagnosis and next steps.

Scheduling is designed to be simple. You can book an appointment online or reach the clinic by WhatsApp with questions before your visit. Whether you’re nearby in Hatillo or traveling from Manatí, Arecibo, Bayamón, or San Juan, EndoInnova offers specialist thyroid care focused on accurate diagnosis and long-term health. Book your appointment with Dr. Mercado today.

How are thyroid conditions diagnosed?

Thyroid conditions are diagnosed with a clinical evaluation plus blood tests measuring TSH, Free T4, Free T3, and thyroid antibodies, with ultrasound added when needed. At EndoInnova in Puerto Rico, endocrinologist Dr. Sheila S. Mercado Méndez interprets these results together with your symptoms to reach an accurate diagnosis.

Diagnosis starts with a conversation, not a lab slip. Dr. Mercado reviews your symptoms — energy, weight, mood, temperature tolerance, heart rate, hair and skin changes — along with your personal and family history, since thyroid disease often runs in families. A physical exam checks the thyroid gland itself for enlargement, tenderness, or nodules.

Blood work is the core of thyroid diagnosis. TSH is the usual starting point, but it rarely tells the whole story on its own. That’s why a thyroid doctor in Puerto Rico often orders a fuller panel: Free T4 and Free T3 show the active hormone levels, while TPO and thyroglobulin antibodies reveal whether an autoimmune process like Hashimoto’s is driving the problem. Reading these together is what separates a screening result from a real diagnosis.

When the exam or labs point to a structural issue — an enlarged gland or a nodule — thyroid ultrasound helps characterize what’s there, and additional evaluation such as a biopsy may be recommended for certain nodules. Occasionally, overlapping causes like low iron or vitamin D are checked, because they can mimic thyroid symptoms.

The value of an endocrinology-led diagnosis is context. Two patients with identical TSH numbers can need very different plans depending on their antibodies, symptoms, and history. Dr. Mercado connects those pieces into a clear picture and explains it in plain language, in English or Spanish. If you suspect a thyroid problem, book an evaluation at EndoInnova in Hatillo for thorough, accurate testing.

What is the difference between hypothyroidism and hyperthyroidism?

Hypothyroidism means an underactive thyroid that makes too little hormone, slowing the body down; hyperthyroidism means an overactive thyroid making too much, speeding it up. Both are diagnosed and treated by an endocrinologist for thyroid in Puerto Rico, with care tailored to the specific condition.

Though they’re opposites, the two conditions are easy to confuse because both cause fatigue and both can affect weight, mood, and heart rate. The direction of the imbalance is what sets them apart.

Hypothyroidism, the more common of the two, happens when the thyroid produces too little hormone — most often due to Hashimoto’s thyroiditis. The body’s processes slow down, causing tiredness, weight gain, cold intolerance, constipation, dry skin, hair thinning, and low mood. Symptoms build gradually, so many people live with them for months before seeking care.

Hyperthyroidism is the reverse: the thyroid makes too much hormone and everything speeds up. Common causes include Graves’ disease and overactive nodules. Signs include unexplained weight loss, a racing or irregular heartbeat, anxiety, tremors, heat intolerance, sweating, and difficulty sleeping. Because it can strain the heart, hyperthyroidism warrants prompt evaluation by a hyperthyroidism doctor in Puerto Rico.

Treatment differs accordingly. Hypothyroidism typically involves replacing the missing hormone and monitoring levels over time. Hyperthyroidism care depends on the cause and may include medication and coordination with other specialists. In both cases, board-certified endocrinologist Dr. Sheila S. Mercado Méndez confirms the diagnosis with the right tests and builds a personalized plan.

Some patients even shift between patterns — early Hashimoto’s can cause a brief overactive phase before settling into underactivity. That’s exactly why endocrinology-led evaluation matters. If you’re unsure which side your symptoms fall on, book an appointment at EndoInnova in Hatillo for clarity.

Can a thyroid problem cause weight gain that won't go away?

Yes — an underactive thyroid can slow metabolism and contribute to weight gain or difficulty losing weight. If diet and exercise aren’t working, a thyroid evaluation with an endocrinologist in Puerto Rico can determine whether your thyroid is a factor before you assume it’s willpower.

Weight and the thyroid are closely linked, but the relationship is often misunderstood. When the thyroid is underactive, metabolism slows, which can lead to modest weight gain, fluid retention, and a frustrating sense that the scale won’t move despite real effort. This is one of the most common reasons patients search for a doctor for unexplained fatigue and weight gain in Puerto Rico — the fatigue and the weight tend to arrive together.

That said, it’s important to have accurate expectations. Hypothyroidism usually accounts for a limited amount of weight, and correcting thyroid levels doesn’t automatically resolve all weight concerns. What treatment can do is remove the metabolic brake, so your efforts with nutrition and activity finally have a fair chance to work. Dr. Sheila S. Mercado Méndez evaluates whether your thyroid is contributing and treats the imbalance as part of the bigger picture.

The reverse also happens: an overactive thyroid can cause unexpected weight loss, which likewise deserves evaluation rather than relief.

Because weight is rarely explained by one cause alone, an endocrinology-led assessment looks at thyroid function, metabolic health, and other factors together. If your thyroid isn’t the driver, EndoInnova also offers dedicated medical weight-management care to address it directly. The first step is simply knowing what you’re dealing with — book a thyroid evaluation at EndoInnova in Hatillo to find out whether your thyroid is part of the story.

What should I expect at my first thyroid appointment?

At your first visit, an endocrinologist for thyroid in Puerto Rico reviews your symptoms and history, examines your thyroid, and orders appropriate blood tests. Dr. Sheila S. Mercado Méndez then explains her findings and outlines a personalized plan — with care available in English or Spanish.

Your first appointment at EndoInnova is meant to be thorough and unhurried. Dr. Mercado begins by listening: how long you’ve had symptoms, how they affect your daily life, what medications or supplements you take, and whether thyroid disease runs in your family. Many patients arrive after feeling rushed or dismissed elsewhere, so this conversation is a priority, not a formality.

Next comes a focused physical exam, including checking the thyroid gland in your neck for enlargement, tenderness, or nodules. Based on your symptoms, Dr. Mercado orders the right blood tests — typically TSH, Free T4, Free T3, and thyroid antibodies — and, if a structural concern is present, may recommend an ultrasound. As a thyroid specialist in Hatillo, she selects tests to fit your case rather than running a generic panel.

You’ll leave understanding what’s being investigated and why. Once results are in, she reviews them with you and explains whether you have hypothyroidism, hyperthyroidism, an autoimmune condition like Hashimoto’s, a nodule, or something else — then discusses the plan in clear terms.

Practical details help too: bring a list of your current medications and any prior thyroid labs, and note your main symptoms beforehand so nothing gets forgotten. Scheduling is straightforward — you can book online or ask questions by WhatsApp in advance.

Whether you’re coming from Hatillo, Manatí, Arecibo, Bayamón, or San Juan, the goal of that first visit is clarity and a plan you understand. Book your appointment with Dr. Mercado at EndoInnova today.

Health Education Made Simple

Understanding your thyroid shouldn’t be complicated. Whether you’re managing a diagnosis or finally looking for answers, endocrinologist Dr. Sheila S. Mercado Méndez gives you clear, personalized guidance for hypothyroidism, hyperthyroidism, Hashimoto’s, and thyroid nodules across Puerto Rico. Book online in minutes—with WhatsApp support for a quick, hassle-free experience.