Unexpected Weight Changes: Could It Be Your Thyroid?

Unexpected weight gain or weight loss can happen for many reasons. While changes in diet, exercise, stress, or hormones are often responsible, an underlying medical condition such as a thyroid disorder may sometimes be involved.

Your thyroid helps regulate your body's metabolism, so changes in thyroid hormone levels can affect how your body uses energy and, in some cases, your weight. However, weight changes alone don't necessarily mean you have a thyroid problem. Looking at your other symptoms can provide important clues.

In this article, we'll explain how your thyroid can affect your weight, the symptoms to look out for, and when it's a good idea to see a GP for an assessment.

How Can the Thyroid Affect Weight?

The thyroid gland produces hormones that are part of a system of tightly regulated neuroendocrine feedback loops that function to regulate the body's metabolism. Thus, changes in thyroid hormone levels influence how your body uses energy and retain water – both of which can affect your weight.  

When thyroid hormone levels are lower than expected, the body’s processes may slow down. This is known as an underactive thyroid, or hypothyroidism. Some people with an underactive thyroid may notice weight gain, tiredness, feeling cold easily or constipation.

When thyroid hormone levels are higher than expected, the body’s processes may speed up. This is known as an overactive thyroid, or hyperthyroidism. Some people with an overactive thyroid may notice weight loss, a faster heartbeat, feeling warm easily, trembling hands or difficulty sleeping.

That said, thyroid-related weight changes usually do not happen on their own. They are often part of a wider pattern of symptoms.

When Weight Gain May Be Linked to an Underactive Thyroid

An underactive thyroid may contribute to weight gain because the body is using energy more slowly than usual. Some people may also feel more sluggish or notice puffiness, bloating or reduced energy.

But weight gain alone does not always mean there is a thyroid problem.

It may be worth speaking to a GP if weight gain happens together with symptoms such as:

• Feeling tired despite getting enough rest
• Feeling unusually cold
• Constipation
• Dry skin
• Hair thinning or hair loss
• Low mood or poor concentration
• Muscle aches or weakness
• Heavier, irregular or prolonged periods
• Cholesterol levels that are higher than expected

These symptoms can develop gradually. Because of that, they may sometimes be mistaken for a busy lifestyle, stress, poor sleep or ageing.

A GP can review your symptoms and decide whether thyroid function should be checked as part of the assessment.

When Weight Loss May Be Linked to an Overactive Thyroid

An overactive thyroid may contribute to weight loss because the body is using energy faster than usual. Some people may lose weight even when their appetite is normal or increased.

It may be worth speaking to a GP if weight loss happens together with symptoms such as:

• A fast, irregular or noticeable heartbeat
• Feeling unusually warm or sweating more than usual
• Trembling hands
• Feeling anxious, restless or irritable
• Difficulty sleeping
• More frequent bowel movements
• Muscle weakness
• Lighter or irregular periods
• A swelling or fullness in the front of the neck

In Singapore’s warm weather, symptoms such as sweating or feeling hot may be easy to brush off. However, if they come with weight loss, palpitations, tremors or sleep changes, it may be useful to get checked.

Weight Changes Can Have Many Causes

This is an important point: weight changes are not always caused by thyroid problems.

While the thyroid can affect weight, it is only one possible factor. Weight gain or weight loss may also be influenced by sleep, stress, appetite, digestion, medication, hormonal changes, blood sugar, mood, life stage, activity levels and other health conditions.

This is why it is helpful not to focus on weight alone. A GP can look at the full picture, including how quickly the weight change happened, whether there are other symptoms, and whether thyroid testing or other health checks may be appropriate.

How a GP Can Help Assess the Full Picture

When you see a GP for unexplained weight gain or weight loss, the consultation is usually about understanding the pattern behind the change.

This may include when it started, how much weight has changed, whether your appetite has changed, and whether there are other symptoms such as tiredness, palpitations, bowel changes, menstrual changes or sleep problems.

Your GP may also ask about:

• Your diet and activity levels
• Sleep and stress
• Medication or supplements
• Past medical history
• Family history of thyroid disease
• Pregnancy or recent childbirth, if relevant

Your doctor may also check your blood pressure, pulse and neck area, especially if there is a visible swelling or a feeling of fullness in the throat.

If thyroid involvement is possible, your GP may recommend a thyroid function blood test.

When to Seek Urgent Medical Attention

Seek urgent medical attention if you have chest pain, severe shortness of breath, fainting, confusion, severe weakness, high fever with agitation, or a rapidly enlarging neck swelling that affects breathing or swallowing.

These symptoms may need prompt medical assessment.

Paying Attention to Unexplained Changes

Unexplained weight gain or weight loss can feel worrying, especially when there is no obvious change in your routine.

Thyroid issues may be one possible factor, but it is not the only explanation. A GP can help review your symptoms, assess your overall health and advise whether thyroid testing or other checks may be appropriate.

If you are concerned about unexplained weight changes, or if your weight change comes with tiredness, palpitations, heat or cold sensitivity, bowel changes, menstrual changes or neck swelling, speak to a GP at Healthway Medical for an assessment.

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