Understanding Hypothyroidism: A Local Look into an Often Missed Condition

“I just felt off—tired, low, and a little foggy—but my labs looked normal,” says Ms. Kim, a 45-year-old teacher from Gangnam. “I never thought it could be my thyroid.”

At Sangdo Woori Internal Medicine, stories like Ms. Kim’s are all too common. Hypothyroidism—an underactive thyroid—often develops slowly, with vague symptoms that patients and even physicians may attribute to stress, aging, or hormonal shifts. Yet this frequently underdiagnosed condition can significantly affect energy, mental clarity, metabolism, and overall quality of life.

In South Korea, thyroid conditions are not rare. Due in part to high health literacy and access to screening, thyroid nodules and hormone imbalances are often detected early—but symptoms can still go unnoticed, especially when TSH and Free T4 levels fall in the “borderline” range. That’s why a nuanced clinical approach is critical.

What Is the Thyroid—and Why It Matters

The thyroid gland is a small, butterfly-shaped organ at the base of your neck. Despite its size, its role in health is massive: it regulates the body's metabolism by releasing hormones—primarily thyroxine (T4) and triiodothyronine (T3). These hormones influence virtually every organ system, controlling how the body uses energy, how fast the heart beats, and how the brain functions.

When the thyroid is underactive, the whole system slows down. Dr. Yoo Du-yeol, the lead internist at Sangdo Woori Internal Medicine, explains:

Early Signs: Often Missed or Misread

The early phase of hypothyroidism is easily mistaken for everyday fatigue or lifestyle exhaustion. That’s especially true for busy professionals, caregivers, and new parents who may assume their symptoms are just part of a hectic schedule.

Common early signs include:

• Persistent fatigue, even after sleeping 7–8 hours

• Increased sensitivity to cold, especially in extremities

• Unexplained weight gain that doesn’t respond to diet or exercise

• Difficulty concentrating, described as “brain fog”

• Dry, flaky skin and brittle nails

• Thinning hair or hair loss, particularly on the scalp and eyebrows

• Mild depression or emotional dullness

• Reduced sweating and lower body temperature

Often, these symptoms appear in combination rather than in isolation. Patients may notice their energy level dropping over several months, followed by changes in skin texture or mood that gradually affect their daily life.

“Fatigue is one of the most reported complaints in our hypothyroid patients,” says Dr. Yoo. “But when fatigue comes with cold intolerance or mental sluggishness, that’s when we start investigating the thyroid.”

Progressing Symptoms: When the Body Slows Further

As hypothyroidism becomes more pronounced, it can affect multiple organ systems. This progression is often slow and overlooked—especially when symptoms are spaced out over months or years.

Mid-stage or moderate hypothyroidism can include:

• Hoarseness, due to fluid retention affecting the vocal cords

• Facial puffiness, particularly around the eyes

• Slowed heart rate, which may cause lightheadedness or fatigue on exertion

• Constipation, linked to slowed gastrointestinal motility

• Joint and muscle pain, stiffness, or heaviness in the limbs

• Menstrual irregularities, such as longer, heavier periods or skipped cycles

• Loss of the outer third of the eyebrows (Sign of Hertoghe)

• Reduced libido or sexual dysfunction in both men and women

These symptoms can interfere with daily functioning and are often misdiagnosed as perimenopausal changes, depression, or chronic fatigue syndrome.

Severe Forms: Rare but Critical

In rare cases, untreated hypothyroidism can become life-threatening. Severe hypothyroidism leads to a condition known as myxedema, where fluid accumulates in the skin and other tissues. Myxedema can cause:

• Thickened skin, especially on the face and limbs

• Swelling of the tongue and vocal cords, affecting speech

• Profound fatigue, slowed reflexes, and cognitive dullness

• Low body temperature and slow respiratory rate

If not treated promptly, this may develop into myxedema coma, a medical emergency characterized by unconsciousness, dangerously low body temperature, and respiratory depression. While extremely rare in Korea due to accessible diagnostics and treatment, it underscores the need for early detection.

“Even mild hypothyroidism can reduce quality of life. Our goal is to catch and treat it long before it becomes dangerous,” says Dr. Yoo.

Why Does It Happen?

In iodine-sufficient countries like South Korea, the leading cause of hypothyroidism is Hashimoto’s thyroiditis, an autoimmune disorder where the immune system gradually damages the thyroid gland.

Other causes include:

• Surgical removal of the thyroid (often for nodules or cancer)

• Radioactive iodine therapy for hyperthyroidism

• Medications that interfere with thyroid hormone production, such as amiodarone or lithium

• Congenital hypothyroidism, though rare

• Secondary hypothyroidism caused by pituitary or hypothalamic dysfunction

Dr. Yoo notes that autoimmune thyroid disease often runs in families. A family history of lupus, rheumatoid arthritis, or Hashimoto’s increases personal risk.

When to Suspect Hypothyroidism

Because hypothyroidism is gradual and subtle, it often takes a combination of symptoms to raise concern.

You should consider screening if you notice:

• Fatigue that worsens despite rest

• Gaining weight without increased food intake

• Constipation, dry skin, or hair thinning

• Feeling colder than others around you

• Depression or mental sluggishness

• Irregular or heavy menstrual periods

• A family history of thyroid or autoimmune disease

• Fertility issues or postpartum emotional changes

“We often hear, ‘I didn’t feel sick, I just didn’t feel right,’” Dr. Yoo shares. “That’s when we explore further—because numbers alone don’t tell the whole story.”

Diagnosis: Going Beyond One Test

Thyroid function testing is straightforward but requires careful interpretation. The standard panel includes:

• TSH (Thyroid Stimulating Hormone) – This hormone rises when the thyroid is underactive, making it a sensitive early indicator.
• Free T4 (thyroxine) – Measures the active thyroid hormone in circulation.
• Anti-TPO antibodies – Helps diagnose Hashimoto’s disease.

Sometimes a person’s TSH may be borderline while symptoms are significant. This is called subclinical hypothyroidism, and it may still warrant treatment, especially if symptoms are disruptive or if antibodies are present.

Follow-up testing every 6–12 weeks is recommended after starting medication or if initial results are inconclusive.

Treatment: Restoring Balance

With the right dose, patients often notice improvements in:

• Energy and concentration

• Mood and sleep quality

• Hair, skin, and digestive health

• Weight stabilization

• Menstrual cycle regularity

“Some patients do best on standard doses, while others need fine adjustments. Our clinic emphasizes collaborative treatment, where we regularly reassess and listen.”

Why Early Attention Matters

Left untreated, hypothyroidism may lead to complications such as:

• Elevated cholesterol, increasing heart disease risk

• Cognitive impairment or worsening depression

• Infertility or complications during pregnancy

• Goiter—an enlarged thyroid gland

Proactive management, even in mild or early cases, helps avoid these long-term issues and enhances overall well-being.

Personalized Care in Seoul

At Sangdo Woori Internal Medicine in Seoul, thyroid care goes beyond just numbers on a lab report. Dr. Yoo Du-yeol and his team provide:

• Thorough diagnostic interviews, listening for subtle clues in your story

• Contextual lab interpretation, combining test results with lifestyle and symptom analysis

• Tailored hormone replacement regimens based on your unique needs

• Ongoing monitoring and support, including medication adjustments and lifestyle counseling

Feeling Off? Let’s Talk

If you’re experiencing a cluster of symptoms—low energy, unexplained weight gain, cold sensitivity, or mood changes—it’s worth a conversation.

Here’s what you can do today:

• Ask your physician for a TSH + Free T4 test

• Share your full symptom history, even if it seems unrelated

• Commit to regular follow-ups every 6–12 months if diagnosed

• Explore support groups or Korean-language wellness resources for thyroid patients

• Seek care from a clinic that listens to your full story—not just your numbers

TL;DR: What to Watch For

• Early signs: fatigue, cold intolerance, brain fog, dry skin, weight gain
• Intermediate signs: hoarseness, menstrual changes, joint pain, puffy face
• Severe signs: swelling, slow breathing, myxedema coma (very rare)
• Tests: TSH, Free T4, anti-TPO
• Treatment: daily thyroid hormone replacement, monitored regularly
• Care at Sangdo Woori: personalized, empathetic, expert-guided