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Baylor Scott & White Endocrinology Specialists McKinney

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8 a.m. - 5 p.m.
8 a.m. - 5 p.m.
8 a.m. - 5 p.m.
8 a.m. - 5 p.m.

Endocrine and metabolic disease care conveniently located in McKinney


Baylor Scott & White Endocrinology Specialists – McKinney is located in McKinney, TX. Vivienne Yoon, MDJennifer St. John, MD, and Sana Ullah, MD, are board certified in internal medicine, endocrinology, diabetes and metabolism.

At BSW Endocrinology Specialists – McKinney, we realize the importance of involving our patients in their treatment plan. We strive to offer innovative management and treatment options that are individualized according to our patient's specific condition.

At this time we are only accepting physician-to-physician referrals.

Pay Your Bill

We offer an easy, secure way to pay your HTPN bill online through MyBSWHealth.

Tools & Resources

Our services are designed with you in mind so managing your healthcare needs is as simple as possible.

  • Patient Forms
  • Appointment Information
  • MyBSWHealth
  • Pay Your Bill
  • Financial Assistance
  • Accepted Insurance

Patient Forms

New Patient Registration Forms

Authorization Forms

We do not release your medical information without your authorization.

Appointment Information

Prescription Refills

Please have your pharmacy fax request for prescription refills to 469.800.5388.

Prepare for Your Visit

If you feel you might have an endocrine or metabolic disorder, make an appointment with your primary care provider. Below is information to help you get ready for your appointment, and what to expect from your doctor.

  • Write down your symptoms, including when they started and how often they occur.
  • List your key medical information, including any other conditions for which you're being treated and the names of any medications, vitamins or supplements you're taking.
  • Log details about your recent diabetes management, if you have diabetes. Notes for your doctor should include the timing and results of recent blood sugar tests, as well as the schedule on which you've been taking your medications if any.
  • List your typical daily habits, including alcohol intake, meals, and exercise routines.
  • Take a family member or friend along, if possible. Sometimes it can be difficult to soak up all the information provided to you during an appointment. Someone who accompanies you may remember something that you missed or forgot.
  • Write down questions to ask your doctor. Creating your list of questions in advance can help you make the most of your time with your doctor.​​​

Questions to ask your doctor if you have diabetes include:

  • Are my signs and symptoms due to hypoglycemia?
  • What is most likely triggering my hypoglycemia?
  • Do I need to adjust my treatment plan?
  • Do I need to make any changes to my diet?
  • Do I need to make any changes to my exercise routine?
  • What else do you recommend to help me better manage my condition?

Questions to ask if you haven't been diagnosed with diabetes include:

  • Is hypoglycemia the most likely cause of my signs and symptoms?
  • What else might be causing these signs and symptoms?
  • What tests do I need?
  • What are the possible complications of this condition?
  • How is this condition treated?
  • What self-care steps, including lifestyle changes, can I take to help improve my signs and symptoms?
  • Should I see a specialist?

In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions during your appointment.

What to Expect from Your Doctor

A doctor who sees you for signs and symptoms of endocrine or metabolic disorder is likely to ask you a number of questions.

The doctor may ask:

  • When did you first notice these signs and symptoms?
  • When do your signs and symptoms typically occur?
  • Does anything seem to provoke your signs and symptoms?
  • Have you been diagnosed with any other medical conditions?
  • What medications are you currently taking, including prescription and over-the-counter drugs as well as vitamins and supplements?
  • What is your typical daily diet?
  • Do you drink alcohol? If yes, how much?
  • What is your typical exercise routine?

Note: If you have diabetes, your doctor may also ask a number of detailed questions about your diabetes management. It will help to come to your appointment with a recent log of blood sugar test results, medication names and schedules, and any changes you've noticed in the frequency or severity of diabetes-related symptoms.


MyBSWHealth is an online tool where you can communicate with your providers, schedule an appointment, access and manage your family’s health.

Pay Your Bill

We offer an easy, secure way to pay your HTPN bill online through MyBSWHealth.

Financial Assistance

At Baylor Scott & White Health, we want to be a resource for you and your family. Our team of financial counselors is here to help. We encourage you to speak to a member of our team at any time – before, during or after care is received.

Accepted Insurance

Baylor Scott & White has established agreements with several types of insurances in an effort to make sure your health needs are covered.

Diseases and Treatments

Baylor Scott & White Endocrinology Specialists – McKinney offers expertise and treatment options conveniently located near you.

  • Adrenal Disease
  • Atherosclerosis Assessment
  • Bone Density Testing
  • Calcium Disorders
  • Cushing's Syndrome
  • Diabetes Mellitus
  • Dietary Counseling
  • Endocrinology
  • Glucose Monitoring
  • Insulin Pump
  • Lipoprotein/Cholesterol Analysis
  • Osteoporosis
  • Parathyroid Disorders
  • Thyroid Cancer
  • Thyroid Disorders

Adrenal Disease

The adrenal glands, located above the kidneys, are responsible for producing hormones such as cortisol and aldosterone, which help the body handle stress and fight illnesses.  The adrenal disease occurs when the adrenal glands fail to produce enough hormones.  This is treated by medication that restores hormones to the correct levels.  Symptoms of the adrenal disease include:

  • Weight loss
  • Craving salt
  • Loss of appetite
  • Excessive fatigue

Atherosclerosis Assessment

What Is Atherosclerosis?

Atherosclerosis is the thickening or hardening of the arteries caused by a buildup of plaque in the inner lining of an artery.  Plaque is made up of deposits of fatty substances, cholesterol, cellular waste products, calcium, and fibrin.  As plaque builds up, the art e r y walls become thickened and stiff.  Atherosclerosis, progressive disease that may start as early as childhood.  However, it can progress rapidly.

​​What are the risk factors?

  • High cholesterol and triglyceride levels
  • High blood pressure
  • Smoking
  • Type 1 diabetes
  • Obesity
  • Physical inactivity
  • High saturated fat diet

​​​​​What are the symptoms of atherosclerosis?

Signs and symptoms may develop gradually and may be few, as the plaque gradually builds up in the artery.  Symptoms may also vary depending on the affected artery.  However, when a major artery is blocked, signs and symptoms may be severe, such as those occurring with heart attack, stroke or blood clot.  The symptoms of atherosclerosis may look like other heart conditions; see your healthcare provider for a diagnosis. 

How is atherosclerosis diagnosed?

First, a complete medical history and physical exam will be performed.  You may also have one or more of these tests:

  • Cardiac catheterization. With this procedure, a long thin tube (catheter) is passed into the coronary arteries.  X-rays are taken after a dye is injected into an artery to locate the narrowing, blockages, and other abnormalities of specific arteries.
  • Doppler sonography.  A special probe is used to direct sound waves into a blood vessel to evaluate blood flow.  An audio receiver amplifies the sound of the blood moving through the vessel.  Faintness or absence of sound may mean there is a blockage.  This is used to identify narrowing of the blood vessels of the abdomen, neck, or legs.
  • Blood pressure comparison.   Comparing blood pressure measurements in the ankles and in the arms helps determine any constriction in blood flow.  Significant differences may mean blood vessels are narrowed due to atherosclerosis.
  • MUGA/radionuclide angiography.   This is a nuclear scan to see how the heart wall moves and how much blood is expelled with each heartbeat, while the person is at rest.
  • Thallium/myocardial perfusion scan.  This is a nuclear scan given while the person is at rest or after exercise that may reveal areas of the heart muscle that are not getting enough blood. 
  • Computerized tomography or CT.  This is a type of X-ray test that can see if there is coronary calcification that may suggest a future heart problem.    

​​How is atherosclerosis treated?

Your doctor will figure out the best treatment based on:

  • Your age
  • Your overall health and medical history
  • How sick you are
  • How well you can handle specific medications, procedures, or therapies
  • How long the condition is expected to last
  • Your opinion or preference

Treatments may include:

Lifestyle changes - You can change some risk factors for atherosclerosis such as smoking, high cholesterol levels, high blood sugar (glucose) levels, lack of exercise, poor dietary habits, and high blood pressure.

Medicines that may be used to treat atherosclerosis include:

  • Antiplatelet medicines.  These are medicines used to decrease the ability of platelets in the blood to stick together and cause clots.  Aspirin, clopidogrel, ticlopidine, and dipyridamole are examples are antiplatelet medicines.
  • Anticoagulants.  Also called blood thinners, these medicines work differently from antiplatelet medicines to decrease the ability of the blood to clot.  Warfarin and heparin are examples of anticoagulants. 
  • Cholesterol-lowering medicines.  These are medicines used to lower fats (lipids) in the blood, particularly low-density lipid (LDL) cholesterol.   Statins are a group of cholesterol-lowering medicines.  They include simvastatin, atorvastatin, and pravastatin among others.  Bile acid sequestrants - colesevelam, cholestyramine and colestipol - and nicotinic acid are the other types of medicine that may be used to reduce cholesterol levels.  Fibrates may also be prescribed to help improve your cholesterol and triglyceride levels. 
  • Blood pressure medicines.   Several different groups of medicines act in different ways to lower blood pressure.

​​Coronary angioplasty - With this procedure, a long thin tube (catheter) is thread through a blood vessel to the heart where a balloon is inflated to create a bigger opening in the vessel to increase blood flow.  Although angioplasty is done in other blood vessels elsewhere in the body, percutaneous coronary intervention (PCI) refers to angioplasty in the coronary arteries to permit more blood flow into the heart.  There are several types of PCI procedures, including:

  • Balloon angioplasty.   A small balloon is inflated inside the blocked artery to open the blocked area.
  • Atherectomy.  The blocked area inside the artery is shaved away by a tiny device on the end of a catheter.
  • Laser angioplasty.  A laser is used to vaporize the blockage in the artery.
  • Coronary artery stent.   A tiny mesh coil is expanded inside the blocked artery to open the blocked area and is left in place to keep the artery open.  

​​Coronary artery bypass - Most commonly referred to as bypass surgery, this surgery is often done in people who have angina (chest pain) due to coronary artery disease (where plaque has built up in the arteries).  During the surgery, a bypass is created by grafting a piece of a healthy vein from elsewhere in the body and attaching it above and below the blocked area of a coronary artery.  This lets blood flow around the blockage.  Veins are usually taken from the leg or from the chest well.  Sometimes more than one artery needs to be bypassed during the same surgery.  

What are the complications of atherosclerosis?

Plaque buildup inside the arteries reduces the blood flow.  A heart attack may occur if the blood supply is reduced to the heart.  A stroke may occur if the blood supply is cut off to the brain.  Severe pain and tissue death may occur if the blood supply is reduced to the arms and legs.

When should I call my healthcare provider?

If your symptoms get worse or you have new symptoms, let your healthcare provider know.

Bone Density Testing

What Is A Bone Density Test?

A bone density test, also known as bone mass measurement or bone mineral density test, measures the strength and density of your bones as you approach menopause and when the test is repeated sometime later, can help determine how quickly you are losing bone mass and density.  These tests are painless, noninvasive, and safe.  They compare your bone density with standards for what is expected in someone of your age, gender, and size, and to the optimal peak bone density of a healthy young adult of the same gender.  Bone density testing can help to:

  • Detect low bone density before a fracture occurs
  • Confirm a diagnosis of osteoporosis if you have a fracture
  • Predict your chances of fracturing in the future
  • Determine your rate of bone loss or monitor the effects of treatment if the test is conducted at intervals of a year or more

​What Are Some Reasons For Having A Bone Density Test?

If you have one or more of the following risk factors for osteoporosis, you may want to consider having a bone density test:

  • You have already experienced a bone fracture that may be the result of thinning bones.
  • Your mother, grandmother, or another close relative had osteoporosis or bone fractures.
  • Over a long period of time, you have taken medication that speeds up bone loss, such as corticosteroids for treating rheumatoid arthritis, or other conditions, or some anti-seizure medications.
  • You have a low body weight, a slight build, or a light complexion.
  • You have a history of cigarette smoking or heavy drinking.

Calcium Disorders

Calcium is found throughout the body, and it works to strengthen teeth and bones, signal cell processes, aid in muscle contraction, and more.  Calcium disorders occur when the body has too little or too much calcium.  A deficit of calcium is called hypocalcemia, which occurs at the failure of parathyroid, a gland located near the thyroids that regulate calcium levels by secreting parathyroid hormones.  A surplus of the parathyroid hormone, as well as a malignant tumor in the body or excessive vitamin D, can lead to hypercalcemia, which also alters the correct amount of calcium.  Symptoms of these disorders include:

  • Nausea
  • Lethargy
  • Bone pain
  • Polyuria

Mild cases may exhibit none of these symptoms, while severe cases may cause an irregular heartbeat, muscle spasms, and severe low blood pressure.  These disorders are treated by adjusting calcium intake, whether through the diet or through intravenous injections. 

Cushing's Syndrome

Cushing's Syndrome occurs when the levels of cortisol in the body are too high. Cortisol is a hormone that regulates blood pressure, insulin levels, and responses to stress.  Cushing's Syndrome can be caused by extended exposure to corticosteroid medication or by a tumor. It causes weight gain in the upper body and softening and rounding of the face.  Other symptoms include easy bruising, headaches, and fatigue. Depending on the cause, it is treated by adjusting medicine intake or removing a tumor.  Medication adjustment should not be undertaken alone; ask your healthcare provider for help.

Diabetes Mellitus

Diabetes is a disease that causes consistently high blood sugar because the body fails to process or produce insulin.  Insulin enables the body to use or store energy from food.  There is three type of diabetes:

  • Type 1 Diabetes
  • Type 2 Diabetes
  • Gestational Diabetes

Type 1 Diabetes requires regular administration of insulin and careful regulation of blood sugar through eating and exercise.  

Type 2 Diabetes is the most common - 90% of diabetes patients have Type 2- and it is treated with adjustments to diet, exercise, and, in some cases, oral medication.

Gestational Diabetes occurs when women have high blood glucose levels during pregnancy.  Though gestational diabetes sometimes requires medication or insulin treatments, it is often treated with lifestyle changes and careful monitoring. 

Dietary Counseling

Dietary Counseling assists in prevention or treatment of nutrition-related illnesses such as cardiovascular disease, cancer, obesity, diabetes, and hyperlipidemia.

Talk to your healthcare provider for more information.


Our physicians provide consultation, diagnosis, and management of endocrine and metabolic diseases. 

Endocrine disorders involve the body's over -or- underproduction of certain hormones, while metabolic disorders affect the body's ability to process certain nutrients and vitamins.

Procedures and treatments we offer include:

  • Atherosclerosis assessment
  • Bone density testing
  • Dietary counseling
  • Glucose monitoring
  • Insulin pump placement and maintenance
  • Lipoprotein/cholesterol analysis

Conditions we treat include:

  • Calcium and skeleton mineralization and metabolism
  • Diabetes mellitus and obesity
  • Diseases of the parathyroid gland
  • Disorders affecting cholesterol and lipoprotein metabolism in relation to atherosclerosis
  • Disorders affecting the pituitary, thyroid, adrenal cortex and reproductive organs
  • Diseases of the adrenal glands
    • Cushing's syndrome
    • Addison's disease
  • Hypertension due to endocrine causes
  • Hypothyroidism
  • Parathyroid cancer
  • Thyroid cancer

Endocrine disorders include hypothyroidism, diseases of the parathyroid gland, diabetes mellitus,  and ovarian dysfunction (including polycystic ovary syndrome ), among others.  Some examples of metabolic disorders include hyperlipidemia and rickets.

Glucose Monitoring

What Is Blood Glucose Monitoring?

Blood glucose levels (also called blood sugar levels) reflect how well diabetes is being controlled and how well the plan of care (diet, exercise, and medication) is working.  If the blood sugar levels are consistently under control (with levels near normal), diabetes complications may be reduced or even prevented.

How Can Blood Sugar Levels Be Checked?

In proper diabetes management, checking blood glucose levels regularly is very important with current methods of blood sugar monitoring requiring a blood sample.  Monitoring blood sugar can be done at home with a variety of invasive devices to obtain the blood sample (invasive means the penetrations of body tissue with a medical instrument).

A drop of blood is obtained through a finger prick to use on a test strip that is then measured in a monitor.  A finger prick can be done with a small lancet (special needle) or with a spring-loaded lancet device that punctures the fingertip quickly.  The strip goes into the meter first, that a drop of blood is placed on the tip of the strip that reads the blood sugar level.

Today, there are many types of monitors on the market, ranging in price, ease of use, size, portability, and length of testing time.  Each monitor requires its own type of testing strip.  If correctly used, blood glucose monitors have been found to be accurate and reliable, and most monitors provide results within seconds.  For visually or physically impaired, there are monitors that give verbal testing instructions and verbal test results.  There are glucose monitors available that provide verbal instructions in Spanish and other languages as well.

People with diabetes may have to check their blood sugar levels up to 4 times a day.  Blood sugar levels can be affected by several factors, including the following:

  • Diet
  • Diabetes medication
  • Exercise
  • Stress
  • Illness 

Certain blood glucose monitors are equipped with data-management systems, which means your blood glucose measurement is automatically stored each time.  Some physician offices have computer systems compatible with these data-management systems, which allows the blood sugar level recordings, and other information, to be transferred electronically.  This can be done on your home computer as well.  One advantage of a data management system is the ability to plot a graph on the computer depicting patterns of blood sugar levels.

What Are Healthy Blood Sugar Level Ranges?

Blood sugar levels over 200 mg/dl (mg/dl=milligrams of glucose per deciliter of blood) or under 70 mg/dl are considered unhealthy.  High blood sugar levels that are about 200 mg /dl may be a sign of inadequate levels of insulin, caused by overeating, lack of exercise, or other factors.  Low blood sugar levels that are below 70 mg/dl may be caused by taking too much insulin, skipping or postponing a meal, over-exercising, excessive alcohol consumption, or other factors.  A good range for most people is between 70 and 130 mg/dl.   

Most common symptoms of hyperglycemia (high blood sugar) include:

  • Rapid, unexplained weight loss
  • Feeling sick
  • Intense thirst
  • Increased urination
  • Vomiting
  • Fatigue
  • Blurred vision
  • Fainting

​​​ *Each individual may experience symptoms differently or no symptoms at all.

Most common symptom of hypoglycemia (low blood sugar) include:

  • Hunger
  • Fatigue
  • Shakiness
  • Headaches
  • Confusion
  • Dizziness
  • Sudden moodiness or behavior changes
  • Sweating
  • Pale skin color

Sometimes, none of these warning symptoms appear before a person loses consciousness from low blood glucose; the loss of consciousness is called hypoglycemia unawareness.

*Each individual may experience symptoms differently or no symptoms at all.

Insulin Pump

An insulin pump is a small computerized device that delivers insulin in two ways:

  • In a steady measured and continuous dose (the "basal" insulin)
  • As a surge ("bolus") dose, at your direction, around mealtime.

Doses are delivered through a catheter, a flexible plastic tube, and inserted through the skin into the fatty tissue with the aid of a small needle and is taped in place.

The insulin pump is not an artificial pancreas since you still have to monitor blood glucose levels, but pumps can help some patients achieve better control, and many prefer this continuous system of insulin delivery over injections.

Pumps can be programmed to release small doses of insulin continuously, or a bolus dose close to mealtime to control the rise in blood glucose after a meal.  This delivery system most closely mimics the body's normal release of insulin.

Lipoprotein/Cholesterol Analysis

Controlling Your Cholesterol

Cholesterol is a waxy substance that travels in your blood through blood vessels.  When you have high cholesterol, it builds up in the walls of the blood vessels, making the vessels more narrow.  Blood flow decreases, creating a greater risk for having a heart attack or a stroke.

Good and Bad Cholesterol

Lipids are fats, and blood is mostly water.  Fat and water don't mix, so our bodies need lipoproteins (lips inside a protein shell) to carry the lipids through the bloodstream.  There are two main kinds of lipoproteins:

  • LDL (low-density lipoprotein) is known as "bad cholesterol."  It mainly carries cholesterol delivering it to the body cells.  Excess LDL cholesterol will build up in artery walls, increasing your risk for heart disease and stroke.
  • HDL  (high-density lipoprotein) is known as "good cholesterol."  This protein shell collects excess cholesterol that LDLs have left behind on blood vessel walls, decreasing your risk of heart disease and stroke. 

​​Controlling Cholesterol Levels

Total cholesterol includes LDL and HDL cholesterol, as well as other fats in the bloodstream.  If your total cholesterol is high, follow the steps below to help lower your total cholesterol level:

  • Eat less unhealthy fat
    • Cut back on saturated fats and trans fats by selecting lean cuts of meats, low-fat dairy, and using oils instead of solid fats.  Limit baked goods, processed meats, and fried foods.  A diet that's high in these fats increases your bad cholesterol.
    • Eat about 2 servings of fish per week.  Most fish contain omega-3 fatty acids which help lower blood cholesterol.
    • Eat more whole grains and soluble fiber such as oat bran which lowers overall cholesterol.  
  • Be Active
    • Choose an activity you enjoy.  Walking, swimming and riding a bike are some good ways to be active.
    • Start at a level where you feel comfortable, increasi​ng your time and pace a little each week.
    • Work up to 40 minutes of moderate to high-intensity physical activity at least 3 to 4 days per week.
    • Remember, some activity is better than none. 
    • If you haven't been exercising regularly, start slowly.  Check with your physician to make sure the exercise plan if right for you.
  • Quit smoking.  By quitting, you can improve your lipid levels and lower your risk for heart disease and stroke.
  • Weight management.  If you are overweight or obese, your healthcare provider can work with you to lose weight and lower your BMI (body mass index) to a normal or near-normal level.  Making diet changes and increasing physical activity can help.
  • Take medication as directed.  Many patients need medication to get their LDL levels to a safe level.  Medications to lower cholesterol levels are effective and safe, but taking medication is not a substitution for exercise or watching your diet.  Your physician can tell you whether you might benefit from a cholesterol-lowering medication. 


Osteoporosis is a disease where bones tend to break easily because of a decreased bond mass index.  As people age, their bones lose density faster than they create it.  This process can be sped up by using tobacco, being sedentary, or drinking too much alcohol.  Though osteoporosis is often not noticed until a bone is broken, it is sometimes recognized by loss of height, back pain, or stooped posture.  Treatments include exercising muscles, which increases bone mass density and, in some cases, medication or fall prevention protectors. 

Parathyroid Disorders

The parathyroid glands, located behind the thyroid glands, are responsible for regulating the body's calcium levels. Calcium strengthens the bones, aids in muscle contraction, helps electrical conduction in the heart, and more. This disease occurs when the parathyroid hormone disrupts the levels of calcium in the body by producing too much or too little of the hormone. Hyperparathyroidism occurs when there is too much of the hormone and is often treated by surgical removal of the glands. Hypoparathyroidism is a deficiency of parathyroid hormones. Its symptoms include muscle cramps and spasms, and the condition is treated with vitamin D and calcium supplements.

Thyroid Cancer

Thyroid cancer is when the thyroids—glands located in the lower neck—develop malignant cancer. Most thyroid cancers respond well to treatment—a typical treatment includes surgery to remove the thyroid, radiation, and a hormone pill, each a few weeks apart from each other. If not treated, however, thyroid cancer can spread to the rest of the body. Symptoms include difficulty swallowing, swollen lymph nodes, and a lump in the lower neck that can be felt through the skin. 

Thyroid Disorders

The thyroids, small glands located in the lower neck, can have a range of disorders. One of these is Graves’ disease, which occurs when the immune system mistakenly attacks the thyroids, causing them to overproduce metabolism-regulating hormones. Hashimoto’s disease is when the immune system attacks the thyroids and destroys them. These diseases are treated with hormone pills and, in severe cases, surgery to remove the thyroid glands. Women may deal with specific thyroid issues, such as hypothyroidism during pregnancy (when the thyroids produce low amounts of hormones) or postpartum thyroiditis (when the thyroids are overactive after pregnancy).

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