Thyroid Disorders: Symptoms, Causes, Diagnosis & Treatment

The thyroid is a small, butterfly-shaped gland at the base of your neck, but when it stops working correctly, the effects reach almost every system in the body. Research puts the overall prevalence of thyroid disease in Bangladesh at roughly 10-20% of the general population, and separate cross-sectional studies have found hypothyroidism in about 5-7% of adults in districts like Khulna and Dhaka. Much of this burden traces back to a preventable cause: an estimated 69% of Bangladeshis still have biochemical iodine deficiency, with the highest rates in hilly and flood-prone regions. Because early symptoms are vague — tiredness, weight change, mood shifts — thyroid disorders are frequently missed or blamed on stress. This guide explains how to recognize hypothyroidism and hyperthyroidism, how doctors diagnose them, how they are treated, and when the situation becomes a medical emergency.

What the Thyroid Does, and Why It Malfunctions

The thyroid gland produces two hormones, T4 (thyroxine) and T3 (triiodothyronine), which control how fast your body uses energy — your metabolic rate, heart rate, digestion, body temperature, and even brain development in children. This entire system is regulated by the pituitary gland through thyroid-stimulating hormone (TSH): when thyroid hormone runs low, the pituitary raises TSH to push the thyroid to work harder; when thyroid hormone runs high, TSH drops.

Thyroid disorders generally fall into two opposite patterns:

• Hypothyroidism — an underactive thyroid producing too little hormone.
• Hyperthyroidism — an overactive thyroid producing too much hormone.

The most common underlying causes in adults are autoimmune: the body's own immune system attacks the thyroid, either slowing it down (Hashimoto's thyroiditis, the leading cause of hypothyroidism) or overstimulating it (Graves' disease, the leading cause of hyperthyroidism). In Bangladesh specifically, iodine deficiency remains a major additional driver — older epidemiological data attributed roughly 35% of thyroid disease cases directly to insufficient dietary iodine, with autoimmune conditions and, less commonly, thyroid nodules or tumors accounting for most of the rest. A hospital-based study at Bangabandhu Sheikh Mujib Medical University (BSMMU) found autoimmune thyroid disease in nearly half (48%) of the thyroid patients it examined, underlining how significant the autoimmune component is even in an iodine-deficient population.

Hypothyroidism: Causes and Symptoms

Besides Hashimoto's thyroiditis and iodine deficiency, hypothyroidism can also follow thyroid surgery, radioactive iodine treatment for a previous overactive thyroid, certain medications, or, less commonly, a problem with the pituitary gland itself. Because thyroid hormone affects nearly every organ, the symptom list is broad and often develops slowly over months:

• Persistent fatigue and low energy
• Unexplained weight gain despite no change in eating habits
• Feeling unusually cold (cold intolerance)
• Constipation
• Dry skin and thinning hair
• Numbness or tingling in the hands
• Low mood, slowed thinking, or depression
• Hoarse voice and puffy face
• Heavier or irregular menstrual periods

Because these symptoms overlap heavily with everyday tiredness, depression, or simply "getting older," hypothyroidism is one of the most commonly missed diagnoses in general practice — which is exactly why a blood test, not guesswork, is needed to confirm it.

Hyperthyroidism: Causes and Symptoms

Hyperthyroidism is most often caused by Graves' disease, but it can also result from toxic nodules in the thyroid, thyroiditis (temporary inflammation), or taking too much thyroid hormone medication. Its symptoms tend to be the mirror image of hypothyroidism:

• Rapid or irregular heartbeat (palpitations)
• Unexplained weight loss despite a normal or increased appetite
• Anxiety, irritability, or a persistent shaky feeling (tremor)
• Heat intolerance and excessive sweating
• Difficulty sleeping
• Frequent bowel movements
• Muscle weakness, especially in the thighs and upper arms

Graves' disease can also cause a distinct eye problem — bulging, dryness, redness, or double vision known as Graves' ophthalmopathy — which needs its own specialist follow-up alongside thyroid treatment.

Subclinical Thyroid Disease: The "Borderline" Cases

Not every abnormal thyroid test means the classic disease pattern. Subclinical hypothyroidism is when TSH is elevated but free T4 is still within the normal range — an early or mild form that may or may not need treatment depending on the degree of elevation, symptoms, and other risk factors. Subclinical hyperthyroidism is the reverse: a low or undetectable TSH with normal free T4 and T3. Both patterns are usually picked up incidentally on blood work and should be discussed with a doctor rather than self-diagnosed, since management depends heavily on the individual's age, symptoms, and heart health.

When It Becomes an Emergency: Thyroid Storm

Severe, untreated hyperthyroidism can rarely trigger a life-threatening condition called thyroid storm. Warning signs include a very high fever (around 104-106°F), a heart rate that climbs above 140 beats per minute, agitation, confusion, delirium, or even coma, along with nausea, vomiting, diarrhea, and abdominal pain. Thyroid storm can be fatal in an estimated 30-40% of untreated cases and progresses within hours, so anyone with known hyperthyroidism who develops sudden high fever, a racing heart, and confusion needs emergency hospital care immediately — this is not something to manage at home.

Diagnosis: What the Tests Actually Mean

Thyroid disease is confirmed with blood tests, not symptoms alone:

• TSH (thyroid-stimulating hormone) is the standard first-line screening test. The commonly used normal reference range is roughly 0.4 to 4.2 mIU/L, though your lab's own reference range should always be used to interpret your result. A high TSH points toward hypothyroidism; a low or suppressed TSH points toward hyperthyroidism.
• Free T4 and free T3 are checked alongside TSH to confirm the diagnosis and gauge severity.
• Anti-TPO (anti-thyroid peroxidase) antibodies help identify an autoimmune cause such as Hashimoto's or Graves' disease.
• Thyroid ultrasound is used when a lump or nodule is felt in the neck, to assess its size and characteristics.
• In select cases, a radioactive iodine uptake scan helps distinguish between different causes of hyperthyroidism.

Because a single test in isolation can be misleading — for example, TSH can be temporarily altered by acute illness, pregnancy, or certain medications — a doctor typically interprets these results together rather than off one number.

Treatment

Treating Hypothyroidism

The standard treatment is daily levothyroxine, a synthetic form of T4 that replaces what the thyroid can no longer produce adequately. It is available in Bangladesh under several brand names, including Thyrox, Tyroid, Eltroxin, Jaroxin, Synroid, and Thormon. The dose is individualized — commonly guided by body weight and age — and is usually taken on an empty stomach, at the same time each day, well before food or other medications (particularly iron and calcium supplements, which can interfere with absorption). After starting or adjusting the dose, doctors typically recheck TSH after about 4-6 weeks before making further changes, since it takes time for hormone levels to stabilize. Some people notice temporary hair thinning in the first few months of treatment as the body readjusts — this usually resolves on its own once thyroid levels normalize.

Treating Hyperthyroidism

Hyperthyroidism has three main treatment paths, chosen based on cause, severity, age, and whether the person is pregnant:

• Antithyroid medication — methimazole or carbimazole (sold in Bangladesh as Thyzol, Tapazol, Carbizol, Carbiroid, or Mercazole) are generally the first choice because of a lower risk of liver toxicity. Propylthiouracil (PTU or Thiocil) is usually reserved for the first trimester of pregnancy or for thyroid storm, despite a higher liver-injury risk, because of specific advantages in those situations.
• Radioactive iodine therapy, which gradually shrinks an overactive thyroid.
• Surgery (thyroidectomy), usually reserved for large goiters, suspected malignancy, or when other treatments aren't suitable.

None of these should be started or stopped without a doctor's supervision, since incorrect dosing in either direction can push a patient from one extreme (hyperthyroid) to the other (hypothyroid).

Special Considerations

Pregnancy

Thyroid hormone needs typically rise during pregnancy, and untreated hypothyroidism has been linked to miscarriage, preeclampsia, and impaired fetal brain development. Women already taking levothyroxine often need their dose increased by roughly 20-30% as soon as pregnancy is confirmed — sometimes managed simply by adding two extra weekly doses — with the target TSH kept toward the lower end of the normal range. After delivery, the dose is usually returned to the pre-pregnancy level. Any woman who is pregnant or planning pregnancy and has a personal or family history of thyroid disease should discuss testing with her doctor early.

Children

Thyroid hormone is essential for normal growth and brain development, so hypothyroidism in infants and children is treated promptly. To avoid triggering hyperactivity or agitation, treatment is often started at a lower dose and increased gradually under a pediatrician's close monitoring, with TSH checked frequently — sometimes every couple of weeks — in the early stages.

Elderly Patients and Heart Disease

In older adults, and especially those with existing heart disease, starting levothyroxine at a low dose and increasing it slowly (over several weeks) is standard practice, because correcting thyroid hormone too quickly can strain the heart and provoke chest pain or an irregular heartbeat. Any sudden palpitations or chest discomfort after starting or adjusting thyroid medication should be reported to a doctor promptly.

Thyroid Disease or Something Else?

Because thyroid symptoms overlap with common everyday complaints, it's worth knowing the usual mix-ups. Hyperthyroidism's palpitations, tremor, and sweating are frequently mistaken for an anxiety disorder — the two can coexist, but only a blood test can tell them apart. Hypothyroidism's fatigue, weight gain, and low mood are often attributed to depression, poor sleep, or simply stress; if these symptoms persist despite lifestyle changes, a TSH test is a reasonable next step rather than assuming it is "just tiredness."

Prevention

• Use iodized salt consistently — Bangladesh's universal salt iodization program helped cut goiter prevalence from around 55% in 1993 to about 7% by 2005, showing how effective this single measure is at a population level.
• Know your family history — autoimmune thyroid disease tends to run in families, so a parent or sibling with thyroid disease raises your own risk.
• Get screened if you're in a higher-risk group — women over 60, postpartum women, and anyone with a personal or family history of autoimmune disease should discuss periodic TSH screening with their doctor.
• Don't ignore a neck lump or persistent swelling — have it evaluated rather than waiting to see if it goes away.

When to See a Doctor

• Persistent, unexplained fatigue, weight change, or mood change lasting several weeks
• A lump, swelling, or visible enlargement in the front of the neck
• Heart palpitations, tremor, or unexplained rapid weight loss
• Irregular or unusually heavy menstrual periods without another explanation
• Any of the above during pregnancy or while planning pregnancy
• Emergency: very high fever with a racing heartbeat, confusion, or fainting in someone with known hyperthyroidism — seek immediate hospital care

Sources: Research on thyroid disorder prevalence and iodine deficiency in Bangladesh (including studies conducted at Bangabandhu Sheikh Mujib Medical University), and clinical guidance from the American Thyroid Association and the World Health Organization.