The Role of Thyroid Hormone in Weight Management

Author :-

Dr.Sreejaya

General Medicine & Diabetology

Understanding the Thyroid: A Biotechnological Perspective

The thyroid gland, though small in size, plays a monumental role in regulating the body’s metabolism, energy levels, and overall well-being. Nestled in the front of the neck, this butterfly-shaped gland produces hormones essential for numerous bodily functions. In this blog, we’ll explore the intricate workings of the thyroid gland, its connection to weight regulation, common disorders, diagnostic tests, and effective management strategies.

The Thyroid Gland and Its Functions

The thyroid gland produces two primary hormones: triiodothyronine (T3) and thyroxine (T4). These hormones control metabolism—the body’s ability to convert food into energy. They regulate energy expenditure, impact body temperature, and ensure the proper functioning of vital organs. Every organ has a relationship with the thyroid, to some extent.

A healthy thyroid maintains a balanced basal metabolic rate (BMR), the amount of energy your body uses at rest. Disruption in thyroid function can lead to metabolic issues, significantly affecting weight, energy, and overall health.

The management of thyroid hormones' energy expenditure is crucial to weight regulation. Thyroid disease, including hyperthyroidism and hypothyroidism, is known to alter body weight and resting metabolic rate. However, whether physiological thyroid hormones affect weight loss and recovery is unclear. A few observational prospective studies found inconsistent results linking thyroid hormones or function to weight or BMI changes. Observational studies of thyroid hormones and weight change are challenging due to the diverse and poorly understood reasons for weight change. Few studies have compared thyroid hormones to RMR, a factor related to thyroid function and energy expenditure, during weight fluctuation. Weight-loss studies with known and homogenous causes have yielded little data.

Thyroid Hormones and Metabolism

Thyroid hormones are indispensable for metabolic rate regulation. They influence the breakdown of proteins, fats, and carbohydrates to meet the body’s energy needs. An imbalance can cause noticeable changes in energy levels and weight.

T3 (Triiodothyronine): The more active hormone, responsible for quick energy use.

T4 (Thyroxine): A precursor converted to T3 as needed, ensuring stable energy levels.

Thyroid hormone (TH) regulates normal growth and adult metabolism. We know that thyroid hormone status affects body weight and energy expenditure. Excess thyroid hormone causes hypermetabolism, which leads to increased resting energy expenditure, weight loss, cholesterol reduction, lipolysis, and gluconeogenesis. However, hypothyroidism, characterised by lower thyroid hormone levels, leads to hypometabolism, resulting in weight gain, reduced resting energy expenditure, increased cholesterol, reduced lipolysis, and impaired gluconeogenesis. Excess thyroid hormone (TH) increases lipogenesis and lipolysis, resulting in fat loss. TH controls energy storage and expenditure in metabolic pathways that regulate energy balance. Through the brain, white fat, brown fat, skeletal muscle, liver, and pancreatic functions, TH controls metabolism.

Thyroid Disorders and Weight Changes

The connection between thyroid health and weight management is profound. Thyroid dysfunction can manifest in two main forms:

1. Hypothyroidism

This condition arises from an underactive thyroid, leading to slowed metabolism. Symptoms include weight gain, fatigue, and sluggishness. The body struggles to convert food into energy, resulting in fat accumulation. Patients begin to experience irregularities in their Body Mass Index (BMR). Not only that, but also the less digestion causes stomach and pancreas issues, which trigger subsequent problems.

2. Hyperthyroidism

Conversely, an overactive thyroid speeds up metabolism, causing weight loss, increased appetite, and excessive energy expenditure. Patients suffering from this disease may experience heightened nervousness and muscle weakness, as well as muscle stiffness. Due to their hypersensitivity, these patients occasionally experience hand sweating and vocal cord choking.

Both conditions can affect body composition, leading to muscle loss, fat gain, or an imbalance between the two.

Symptoms of Thyroid Imbalance

Common signs of thyroid dysfunction include:

The symptoms of hypothyroidism include fatigue, weight gain, cold intolerance, dry skin, and depression.
Hyperthyroidism Symptoms: Weight loss, increased appetite, heat intolerance, rapid heartbeat, and irritability.

Fatigue, lethargy, cold intolerance, weight gain, constipation, voice change, and dry skin are the most prevalent symptoms in adults; however, age, sex, and other variables affect clinical presentation. Levothyroxine is the usual treatment.

These symptoms not only impact physical health but also daily life, disrupting sleep, work productivity, and mental well-being. Mostly, obesity is one of the visible symptoms; however, thyroid problems can manifest in various ways, including heartbeat issues, blood pressure problems, and even elevated cholesterol levels.

Diagnosing Thyroid-Related Weight Issues

Proper diagnosis is crucial to managing thyroid disorders. Standard tests include:

TSH (Thyroid-Stimulating Hormone): Indicates overall thyroid function.
Free T3 and T4 Levels: Measure hormone activity in the bloodstream.
Thyroid Antibody Tests: Help identify autoimmune disorders like Hashimoto's or Graves’ disease.

In obesity, no study directly examined hypothyroidism screening benefits. HT is common and can increase obesity-related weight gain and comorbidities; hence, obese individuals should get a basic thyroid function test. The recommended hypothyroidism screening test is TSH. We measure free T4 (FT4) in individuals with elevated TSH levels, suspected thyroid hormone resistance, or anterior pituitary insufficiency. Not more than 1% of HT has secondary hypothyroidism (HT) with low-to-normal TSH and free T4. Hypothyroidism screening benefits from neither total nor free T3. Elevated TSH stimulates remaining thyroid tissue, keeping T3 normal. Nonthyroidal illnesses like nutritional status and inflammatory conditions, which reduce T4 to T3 conversion (called “euthyroid sick syndrome”), also affect FT3 levels. Obese people have higher FT3 levels than lean people, mostly due to nutritional differences.

Regular testing ensures early detection and timely intervention. Early detection can prevent multiple issues, even if some are incurable, but it keeps those that are at least treatable to some extent or arrests the issue without any delay.

Treating Thyroid Disorders for Weight Management

Medications and Hormone Replacement: Synthroid (levothyroxine) for hypothyroidism or antithyroid medications for hyperthyroidism can restore hormonal balance.
Dietary Adjustments: A diet rich in iodine, selenium, and zinc supports thyroid health. Avoid excessive consumption of goitrogens found in soy and cruciferous vegetables.
Exercise: Moderate-intensity workouts enhance metabolism without overtaxing the body.
Stress Management: Techniques like yoga and mindfulness reduce stress, a known thyroid disruptor.

Overt hypothyroidism (HT) or moderate HTH with a TSH level above 10 mIU/L should start THR. The best replacement hormone is L-thyroxine. The combination of L-thyroxine and L-triiodothyronine has no advantages. We measure TSH levels for THR monitoring. If there is no laboratory-specific normal range, we target TSH between 0.45 and 4.12 mIU/L. For treatment monitoring, avoid FT3 and FT4. For older or cardiovascular disease patients with overt HT, a lower beginning dosage and slower dose increase should be considered. In obesity, a modest TSH rise (<10 mIU/L) with normal FT4 is frequent and should not be used to diagnose primary hypothyroidism without thyroid antibodies. Subclinical hypothyroidism progresses to overt hypothyroidism at a rate of 2–5% per year, and this rate is lower in obese individuals. L-thyroxine did not help obese subclinical hypothyroidism patients lose weight in a meta-analysis.

Obese people with modestly elevated TSH levels should not begin thyroid hormone replacement to lose weight. If a person is not overweight and has a slightly elevated TSH level (<10 uIU/L) and a normal FT4 level, they should get thyroid hormone replacement. This is especially important for young people who have thyroid antibodies, a history of destructive thyroiditis, or radioiodine therapy for hyperthyroidism. Consider L-thyroxine during childbearing. Those over 70, particularly those with cardiovascular diseases, should prioritise a follow-up approach. In older patients with subclinical hypothyroidism, the Trust Thyroid Trial found no clinical advantages from levothyroxine therapy, but no research has focused on obese older people. Several investigations found relatively small impacts on weight change, urine nitrogen excretion (showing lean mass loss), bone metabolism, and emotional state. Obesity increases the risk of cardiac arrhythmia, heart failure, and ischaemic events in cardiovascular disease patients.

Childbearing women with subclinical HT are at risk of infertility, pregnancy difficulties, and neonatal neurocognitive impairments. In pregnant women with TSH levels above 4.0 mIU/L, thyroid hormone supplementation reduces pregnancy loss and early birth. For women considering pregnancy and during conception with TSH levels above 2.5 mIU/L and positive blood thyroid peroxidase antibodies, the American Thyroid Association (ATA) advises thyroxine supplementation. Trimester-specific TSH levels (less than 2.5 mIU/L in the first trimester, 3 in the second, and 3.5 in the last) should be the objective for pregnant women. No studies have examined whether obese women have a distinct target TSH range.

Thyroid Cancer and Weight

Thyroid cancer is a less common but serious condition. Symptoms may include a lump in the neck, hoarseness, or unexplained weight changes. Treatments such as surgery, radioactive iodine, and hormone replacement therapy can significantly affect metabolism and weight. Post-treatment recovery requires personalized care to stabilize thyroid function. Obesity is defined as having too much bodily fat. Obesity is associated with cancers such as breast, endometrial, colon, esophageal adenocarcinoma, prostate, liver cell carcinoma, leukaemia, non-Hodgkin lymphoma, and melanoma. Worldwide, obesity is a huge public health concern. The incidence of obesity in Korea has consistently climbed from 28% in 2006 to 32% in 2015, and abdominal obesity from 18% in 2009 to 21% in 2015. Between 1960–1962 and 2011–2012, obesity in the US rose from 13% to 35%. The global prevalence of thyroid cancer has also increased in recent decades.

We eliminated thyroid cancer patients diagnosed during the research period and categorised thyroid cancer as ICD-10 code C73. Fasting blood glucose levels of 126 mg/dL or more (≥7 mmol/L) or annual claims for anti-hyperglycemic drugs with ICD-10 codes E10–14 are used to diagnose diabetes. Hypertension was defined as systolic blood pressure (SBP) > 140 mmHg or diastolic blood pressure (DBP) ≥ 90 mmHg, or the existence of ICD-10 codes I10-I15 anti-hypertensive prescription claims each year. Dyslipidemia was characterized by total cholesterol levels ≥240 mg/dL (≥6.22 mmol/L), LDL cholesterol ≥100 mg/dL (≥2.59 mmol/L), triglycerides ≥150 mg/dL (≥3.88 mmol/L), and HDL cholesterol ≤40 mg/dL. Using self-reporting questionnaires, regular physical activity was more than one moderate- or vigorous-intensity day per week. In our previous study, we used ICD-10 codes (E02, E03, E05, and E06.3) to characterize hypothyroidism and hyperthyroidism, as well as medication and therapy.

Conclusion

Understanding the thyroid gland's pivotal role in metabolism and weight regulation highlights the importance of early detection and proactive management of thyroid disorders. By adopting a combination of medical interventions, dietary adjustments, and lifestyle changes, individuals can optimise thyroid health and improve their quality of life. We recommend that all thyroid patients undergo specialised checkups, and those already experiencing thyroid problems seek expert advice and visit Ovum Hospitals for enhanced healthcare support and expert advice.

FAQs

1 What is the primary role of the thyroid gland in the body?

The thyroid gland regulates metabolism, energy production, and organ function through the production of T3 and T4 hormones.

2 How do thyroid hormones affect weight?

Thyroid hormones control the metabolic rate, influencing how the body uses calories.Hypothyroidism often causes weight gain due to a slowed metabolism, while hyperthyroidism can lead to weight loss due to an accelerated metabolism..

3 What are the common symptoms of thyroid imbalance?

Symptoms of hypothyroidism include fatigue, weight gain, and depression, while hyperthyroidism symptoms include weight loss, rapid heartbeat, and irritability.

4 How are thyroid disorders diagnosed?

Blood tests such as TSH, free T3, free T4, and thyroid antibody tests diagnose thyroid disorders. These help determine the type and severity of the disorder.

5 Can lifestyle changes improve thyroid health?

Yes, a balanced diet rich in essential nutrients, regular exercise, and stress management techniques can support thyroid function and enhance overall well-being.