Thyroid Hormones Are Essential for Energy, Weight and More: What Working Adults Need to Know

Learn how screening thyroid hormones like T4 and TSH can give working adults more energy, better moods, and improved cardiovascular health.

As a working professional, your health and longevity are top priorities. While you're focused on career and family, it's easy to overlook critical markers of wellness that can significantly impact your energy, metabolism, and vitality over the long run.

Two of the most important blood tests for maintaining optimal health as you age are free thyroxine 4 (FT4) and thyroxine stimulating hormone (TSH). These thyroid hormones regulate essential bodily functions and influence everything from your mood and motivation to muscle function and cholesterol levels.

For peak performance and longevity, it's critical to understand how the thyroid works, why regular screening for FT4 and TSH is so important after 40, what ideal levels look like, and how to manage your thyroid health through lifestyle changes and medical interventions if needed. This comprehensive guide provides practical recommendations to empower you with the knowledge and tools to take control of your thyroid health.

TLDR: TSH and FT4 regulate your metabolism, energy levels, and many other bodily functions.

  • Regular screening of two thyroid hormones - free thyroxine 4 (FT4) and thyroxine stimulating hormone (TSH) - after age 40 is important for optimal health, wellness and longevity.
  • Ideal thyroid hormone levels contribute to higher energy, better mood, and improved muscle and cardiovascular function.
  • Lifestyle changes and medical treatment if needed can help manage thyroid health.

Understanding Thyroid Hormones: T4 and TSH

The thyroid hormone thyroxine, often referred to as T4, is produced by the thyroid gland. T4 regulates how quickly the body burns energy and converts food into usable energy. Proper T4 levels are important to maintain a healthy metabolism, regulate growth and development, and produce protein for muscle, bone, and blood production.

Thyroid stimulating hormone (TSH) is a hormone produced by the pituitary gland. The pituitary gland secretes TSH to stimulate the thyroid gland to produce more thyroid hormones like T4 and T3. TSH levels in the bloodstream therefore serve as an indicator of how well the thyroid gland is functioning. High or low TSH levels can indicate hyperthyroidism or hypothyroidism respectively.

Why Thyroid Health Matters for Working Adults

Why Thyroid Health Matters for Working Adults

As a working adult, maintaining optimal thyroid health is essential for your longevity, daily energy, and cognitive performance. Your thyroid produces two key hormones - free thyroxine (FT4) and thyrotropin or thyroid stimulating hormone (TSH) - that regulate your metabolism and impact your health in many ways:

  • Energy levels: Optimal FT4 and TSH maintains a healthy metabolism and helps convert the food you eat into usable energy. With low thyroid hormone levels, your metabolism slows down, reducing energy levels.
  • Weight Changes: An unexplained change in weight can also indicate a thyroid imbalance. Weight gain and difficulty losing weight can be a symptom of hypothyroidism. Hyperthyroidism, or an overactive thyroid, may cause weight loss, sometimes with increased appetite. Thyroid hormones help regulate metabolism, body temperature, and appetite.
  • Mood: Thyroid hormones play a role in regulating neurotransmitters like serotonin and dopamine that influence your mood and motivation. Abnormal thyroid levels can cause depression, anxiety and brain fog.
  • Muscle strength and function: Proper thyroid function supports muscle growth, regeneration and repair. Low T4 levels can lead to muscle weakness, cramps and loss of strength.
  • Cardiovascular health: Your thyroid regulates heart rate and force of cardiac contraction. High or low thyroid hormone levels may strain your heart and increase heart disease risk.
  • Cognitive performance: Thyroid hormones influence neurotransmitter levels, blood flow to the brain and glucose metabolism - all of which impact memory, concentration and mental acuity.
  • Sleep Disturbances: Difficulty falling asleep or excess sleepiness can occur with hypothyroidism or hyperthyroidism. An overactive thyroid may cause insomnia, while an underactive thyroid may lead to excessive sleep and fatigue.

In summary, for working adults seeking to optimize health, productivity, and longevity, maintaining optimal thyroid function through regular screening, lifestyle strategies, and medical management when needed should be a top priority.

Testing Your Thyroid Hormone Levels: When and How Often

To properly monitor your thyroid health, regular testing of your thyroid hormone levels is essential. As a working adult, you should have your thyroid stimulating hormone (TSH) and free thyroxine (FT4) levels checked at least once every 2-3 years, or more frequently if you have a known thyroid condition.

Testing Frequency

The typical recommendation for screening euthyroid individuals (those with normal thyroid function) is to test TSH and FT4 levels every 2-3 years for working adults.

However, if you have symptoms of an overactive or underactive thyroid such as fatigue, mood changes, weight fluctuations or sleep problems, you should consult your physician about testing as soon as possible. They may want to check your levels more often, such as every 6-12 months.

Blood Tests

The most common way to test your thyroid hormones is through a blood test. A blood sample is drawn and sent to a lab to measure the amounts of TSH and FT4, the two hormones primarily responsible for regulating your metabolism and energy levels.

Target Levels

For working adults without a known thyroid condition, ideal TSH levels generally fall between 0.5 to 2.0 mIU/L, while normal FT4 levels tend to range from 0.8 to 1.8 ng/dL. However, target levels can vary based on factors like age, so you should discuss your individual results with your physician. They may want to investigate further or make adjustments to lifestyle, diet or medication to bring your hormones back into the optimal range.

Through regular screening and maintaining thyroid hormone levels in balance, you can continue to enjoy stable energy, metabolism and overall health and wellness for years to come.

Mito Health's flagship package, priced at $499, offers testing for FT4, TSH as well as 65 other carefully curated biomarkers that provide insight into various aspects of your health - this comprehensive suite of tests allows for early detection of cancer, heart disease, neurodegenerative disorders, diabetes and more. 

In addition to testing, you will receive a personalized health optimization plan from our doctors incorporating supplements, nutrition, exercise and sleep strategies, discounted pricing for specialized additional tests, and access to exclusive health and longevity events.

Lifestyle Changes to Support Thyroid Health

To support your thyroid health and hormone balance as a working adult, making certain lifestyle changes can have a significant impact.

Reduce Chronic Stress

Chronic stress can negatively impact your thyroid function over time. Engage in regular stress management techniques like yoga, meditation, deep breathing, or journaling. Limiting stressful activities when possible and spending time with loved ones can also help.

Prioritize Sleep

Most adults need 7 to 9 hours of sleep per night to feel well-rested. Lack of sleep can disrupt your thyroid hormone levels and metabolism. Go to bed and wake up at the same time each day, limit screen time and blue light exposure before bed, and make your bedroom as dark as possible for the best sleep environment.

Exercise Regularly

Exercise provides many benefits for your thyroid health. Aim for 30 to 60 minutes of moderate activity most days of the week. Walking, biking, strength training, and yoga are all excellent options. Exercise helps stimulate your thyroid gland and increases tissue sensitivity to thyroid hormones. It also boosts metabolism and supports weight management.

Key Nutrients and Foods for Thyroid Support

To support your thyroid health through nutrition, focus on key nutrients and foods that provide the building blocks for thyroid hormones.


Iodine is essential for the production of thyroid hormones T3 and T4. The recommended daily intake of iodine for most adults is 150 mcg per day. Good sources of iodine include:

  • Seaweed (like nori, kombu, and wakame)
  • Saltwater fish (such as cod, tuna, and perch)
  • Dairy products (especially yogurt and cheese)
  • Eggs
  • Prunes


Selenium helps convert T4 into the active hormone T3. The recommended daily intake is 55 mcg for most adults. Food sources high in selenium include:

  • Brazil nuts
  • Sardines
  • Grass-fed beef
  • Turkey
  • Barley


Zinc is essential for the synthesis and release of thyroid hormones. The recommended daily intake is 8-11 mg for most adults. Zinc-rich foods include:

  • Oysters
  • Pumpkin seeds
  • Cashews
  • Chickpeas
  • Grass-fed beef


Iron helps transport oxygen in your blood and tissues, including those involved in thyroid function. For most adults, the recommended daily intake is 8-18 mg. Good sources of iron include:

  • Grass-fed red meat
  • Poultry (especially duck and turkey)
  • Seafood (like clams, sardines, and tuna)
  • Legumes (such as lentils, beans, and chickpeas)
  • Dark leafy greens (such as spinach, Swiss chard, and kale)

In summary, consuming a balanced diet with adequate iodine, selenium, zinc, and iron can help support your thyroid health and hormone production. Focus on whole foods like seafood, nuts, seeds, legumes, and high-quality animal proteins. Limit excess sugar and refined grains, which can interfere with nutrient absorption.

Thyroid Medications and Supplements

If your thyroid hormone levels are not in the normal range, your doctor may prescribe thyroid medication or supplements to help regulate them. The most common medications for hypothyroidism (underactive thyroid) are:

Levothyroxine (Synthroid®, Levoxyl®, Unithroid®)

This is a synthetic version of the T4 hormone. It is the standard treatment for hypothyroidism. The dosage is adjusted based on follow-up blood tests until your TSH and T4 levels stabilize in the normal range. Most patients remain on the same dosage for many years.

Liothyronine (Cytomel®)

This synthetic T3 hormone is sometimes added to T4 therapy or used alone if T4 alone does not resolve symptoms. T3 medications have a shorter half-life so dosages need to be more closely monitored with blood tests.

For hyperthyroidism (overactive thyroid), common antithyroid medications include:

Methimazole (Tapazole®)

This prevents the thyroid from producing excess hormones. It is usually the first-line treatment for hyperthyroidism. Side effects can include rash, hives, and liver inflammation.

Propylthiouracil (PTU)

This also prevents excess hormone production but may cause more side effects. It is usually only used if methimazole cannot be tolerated or during pregnancy.


In conclusion, your thyroid health is closely tied to how you feel and function each day. By understanding the importance of FT4 and TSH levels, you have taken an important first step to supporting your longevity and wellbeing. Don't settle for subpar health or assume declining energy is just a normal part of aging.

At Mito Health, we specialize in advanced health diagnostics to test your thyroid hormone levels (along with 65 other biomarkers) - to form a science-based, personalized health plan to help you optimize your health. Sign up for our flagship package today to take control of your health and your future. 

Written By
J. Hsu
December 29, 2023
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The information provided by Mito Health is for improving health and wellness only, and not to be taken as medical advice or medical recommendations.

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