24/07/2026
When your thyroid hormones are too high or too low
Unexplained fatigue, weight gain without a clear cause, or a racing heartbeat, may be signs of a thyroid disorder โ one of the most common endocrine diseases affecting Malaysians.
The thyroid gland, located at the base of the neck, plays a crucial role in regulating metabolism, growth and electrolyte balance in the blood through the secretion of thyroid hormones.
A thyroid disorder occurs when the production of these hormones is disrupted.
The two main types of thyroid disorders are hyperthyroidism, which involves excessive thyroid hormone production, and hypothyroidism, which occurs when hormone production is insufficient.
Thyroid disorders are more common in women than in men, with studies showing that women are five to 20 times more likely to develop these conditions.
This higher occurrence is linked to hormonal changes, pregnancy and a greater susceptibility to autoimmune diseases.
Globally, hypothyroidism affects about 1-2% of individuals, with the risk increasing with age, particularly among women.
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Hyperthyroidism, however, is less common, affecting 0.5-2% of women, primarily caused by autoimmune conditions.
In Malaysia, the frequency of hypothyroidism is approximately 2.1%, while hyperthyroidism affects about 3.4% of the population.
Too little hormone
Hypothyroidism, or an underactive thyroid, often occurs due to several factors.
These can include an autoimmune attack on the thyroid gland, previous treatment with radioiodine, or surgery to remove the thyroid gland.
In addition, certain medicines, such as lithium (an antipsychotic) and amiodarone (used to treat irregular heart rhythm), may also contribute to the development of hypothyroidism.
Patients with hypothyroidism typically present with a distinct set of signs and symptoms.
As a result of insufficient thyroid hormone production, the bodyโs metabolism slows down, leading to symptoms such as dry skin, poor memory, slowed thinking, fatigue, weight gain, cold intolerance and constipation.
The mainstay of treatment is levothyroxine, a synthetic form of the thyroxine (T4) hormone.
The dosage is tailored to individual needs based on thyroid function test results to ensure appropriate hormone replacement.
Levothyroxine acts as a substitute for the natural T4.
Once absorbed, it is converted into the active hormone that regulates the bodyโs metabolism and other essential functions.
For optimal absorption, levothyroxine should be taken in the morning on an empty stomach at least one hour before breakfast, or at bedtime at least three hours after the last meal of the day.
This is as food can interfere with its absorption.
In addition, it should not be taken within four hours of consuming any calcium- or iron-containing products.
Common side effects of levothyroxine may include palpitations, exercise intolerance, tachycardia (fast heart rate), shortness of breath on exertion, weight loss and insomnia.
Too much hormone
Hyperthyroidism, or an overactive thyroid, arises from several underlying causes.
The most common is an overactive immune system, as seen in Gravesโ disease.
Other causes include abnormal growths in the thyroid gland, such as toxic multinodular goiter and small non-cancerous lumps known as thyroid adenomas.
Several risk factors have been identified, including genetic predisposition, psychological stress, smoking and being a female.
Clinically, patients with hyperthyroidism present with a distinct set of symptoms driven by an increased metabolic rate.
These include unintentional weight loss, heat intolerance, palpitations, tremors and hyperactivity.
In terms of management, the main treatment options for an overactive thyroid include antithyroid medicines, radioactive iodine therapy, and in certain cases, surgery.
Antithyroid medicines such as carbimazole and propylthiouracil are commonly used to reduce thyroid hormone production.
Carbimazole inhibits the enzyme thyroid peroxidase, thereby reducing the synthesis of new thyroid hormones.
Importantly, carbimazole does not affect thyroxine that has already been produced and stored in the thyroid gland.
As a result, it may take approximately four to eight weeks of treatment before thyroid hormone levels return to normal.
In contrast, propylthiouracil not only decreases hormone production, but also blocks the conversion of thyroxine (T4) into the more active triiodothyronine (T3), which plays a key role in regulating metabolism.
For treatment to be effective, these medicines must be taken consistently at the same time each day, with regular monitoring of thyroid function.
Careful monitoring is essential as these medicines may cause serious adverse effects, including a significant reduction in white blood cell count and liver damage.
Other adverse effects may include itchy skin, joint pain, and gastrointestinal symptoms such as nausea, bloating, diarrhoea and abdominal discomfort.
Notably, in pregnant women, propyl- thiouracil is the preferred option during the first trimester due to rare safety concerns regarding potential birth defects associated with carbimazole.
If symptoms are not adequately controlled with medicines, radioactive iodine (I-131) therapy may be considered as the next line of treatment.
This therapy works by gradually destroying overactive thyroid cells, thereby reducing hormone production.
It can be administered orally as a capsule or liquid, or intravenously.
However, patients should be informed that this treatment may lead to hypothyroidism, and in some cases, thyroid-related eye disease.
Patients, take note!
For patients diagnosed with thyroid disorders, adherence to prescribed medicines is crucial for maintaining stable thyroid function.
Missing doses may lead to symptom recurrence and potential complications.
In addition, it may take several months before noticeable improvement occurs and blood test results return to normal.
Therefore, regular follow-up and blood tests are essential to monitor for side effects and ensure optimal management.
Patients are also advised to inform their doctor if they are pregnant, as the choice and dosage of medicines may need to be adjusted.
In conclusion, thyroid disorders are common conditions that can significantly affect quality of life if left untreated.
Therefore, increasing public awareness and adhering to treatment are essential for effective management.
Ultimately, close communication between patients and healthcare providers plays a vital role in maintaining optimal thyroid function and overall well-being.
Woon Shiau Mei is a pharmacist at Hospital Shah Alam, Selangor. This article is courtesy of the Health Ministryโs Pharmacy Practice and Development Division.
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