° the relationship between hypothyroidism and obesity °<br /><br /><br />Thyroid hormone is the hormone that’s mainly responsible for controlling the speed of your body’s metabolism. In infants, thyroid hormone is critical for brain development. Your thyroid, a small, butterfly-shaped gland located at the front of your neck under your skin, releases thyroid hormone. It’s a part of your endocrine gland. organs in your body transform T4 into T3 so that it can impact your cells and your metabolism.<br /><br /> <br /><br /><br /><br /><br /><br /><br /><br />Your thyroid also releases a hormone called calcitonin to help regulate calcium levels in your blood by decreasing it. Calcitonin isn’t grouped into the “thyroid hormone” name, and it doesn’t impact your body’s metabolism like T3 and T4 do.<br /><br />The functions of the thyroid hormones :<br />● Increases the basal metabolic rate<br />● Depending on the metabolic status, it can induce lipolysis or lipid synthesis.<br />● Stimulate the metabolism of carbohydrates<br />● Anabolism of proteins. Thyroid hormones can also induce catabolism of proteins in high doses.<br />● Permissive effect on catecholamines<br />● In children, thyroid hormones act synergistically with growth hormones to stimulate bone growth.<br />● The impact of thyroid hormone on CNS is important. During the prenatal period, it is needed for the maturation of the brain. In adults, it can affect mood. Hyperthyroidism can lead to hyperexcitability and irritability. Hypothyroidism can cause impaired memory, slowed speech, and sleepiness.<br />● Thyroid hormone affects fertility, ovulation, and menstruation.<br /> <br />Key Mechanisms Linking Hypothyroidism and Obesity<br />1. Reduced Basal Metabolic Rate (BMR)<br /><br />○ Thyroid hormones (T3 and T4) regulate energy expenditure. When thyroid hormone levels are low, the body burns fewer calories, leading to weight gain.<br />○ Studies suggest that BMR can drop by 10-25% in hypothyroid patients.<br />2. Increased Fat Accumulation<br /><br />○ Hypothyroidism alters lipid metabolism, causing increased fat storage.<br />○ It raises LDL cholesterol and triglyceride levels, contributing to obesity-related metabolic issues.<br /><br />3. Appetite and Hormonal Changes<br /><br />○ Some patients with hypothyroidism experience increased appetite, leading to excessive calorie intake.<br />○ Hypothyroidism affects leptin and ghrelin (hunger-regulating hormones), sometimes disrupting appetite control.<br />○ Leptin is a hormone, made by fat cells, that decreases your appetite. <br />○ Ghrelin is a hormone that increases appetite, and also plays a role in body weight.<br />○ Hypothyroidism is the most common medical conditions associated with high levels of leptin, as well as with another condition described as leptin resistance<br />○ Leptin resistance is a diminished response to leptin, even if there is enough of it circulating throughout the body. This resistance is based on a false message that the body is starving and, thus, multiple hormonal mechanisms are activated to increase fat stores, as the body tries to reverse the perceived state of starvation. Even with a moderate caloric intake, this is believed to increase the risk of weight gain or obesity.<br />○ The mechanisms that are activated by leptin resistance, all of which result in weight gain, include:<br />○ Diminished TSH secretion.<br />○ Suppressed thyroxine (T4) to active triiodothyronine (T3) conversion.<br />○ Increased reverse T3 production.<br />○ Increased appetite.<br />○ Increased insulin resistance.<br />○ Inhibition of lipolysis (fat breakdown).<br />4. Insulin Resistance<br /><br />○ Insulin resistance is a physiological state where your blood sugar is elevated either through carbohydrate intake that is too high for your current capacity, as well as stress, another thing that can raise your blood sugar. When that happens, your pancreas will secrete insulin to package that blood sugar and bring it to your muscle tissues and liver.<br />○ Thyroid hormones play a crucial role in regulating metabolism, including the breakdown and utilization of glucose in the liver and muscles. When thyroid hormone levels are low, as in hypothyroidism, the body’s ability to effectively use glucose for energy can be compromised. Elevated blood sugar levels can develop, along with increased insulin production, ultimately resulting in insulin resistance.<br />5. Altered Brown Adipose Tissue (BAT) Function<br /><br />○ There are different types of fat in your body. Healthcare providers identify each type of fat by its color and function, including:<br />○ White fat: Most of the fat in your body is white fat. White fat stores energy in various places around your body. White fat insulates your organs. Too much white fat leads to obesity.<br />○ Brown fat: Brown fat is smaller than white fat. It stores energy and burns that energy to regulate your body temperature. Brown fat helps you burn calories by creating heat right before your body starts to shiver (thermogenesis). It also helps regulate sugar (glucose) and fat metabolism.<br />○ Beige fat: Beige fat is a combination of white and brown fat cells. These cells burn calories to regulate body temperature by converting white fat cells to brown.<br />○ The function of the Brown fat is responsible for producing heat to warm the blood in your body. You’ll notice brown fat burning right before you start to shiver because the fat activates (turns on) in cold temperatures. It produces heat by breaking down blood sugar (glucose) and molecules of fat. This process (thermogenesis) creates heat to help you maintain your body temperature.<br />○ Brown fat helps in burning calories, and thyroid hormones stimulate its activity. Hypothyroidism impairs BAT function, contributing to weight gain.<br /> <br /><br /><br />Does Hypothyroidism Always Cause Obesity?<br />Not necessarily. Mild hypothyroidism may not cause significant weight gain, and many obese individuals have normal thyroid function. Additionally, weight gain in hypothyroidism is often modest (around 2-5 kg) and primarily due to water retention rather than fat accumulation.<br /><br />Impact of Treating Hypothyroidism on Obesity<br />● Thyroid hormone replacement therapy (Levothyroxine): Can help normalize metabolism and reduce some weight, but it does not guarantee significant weight loss.<br />● Diet and Exercise: Remain crucial for managing weight in hypothyroid individuals.<br />● Metabolic Adjustments: Even after treatment, some patients struggle with weight due to long-term metabolic adaptations.<br /><br />Conclusion<br />Hypothyroidism can contribute to weight gain, but it is not the sole cause of obesity. The interaction between thyroid function and body weight is influenced by metabolic rate, hormone regulation, fluid retention, and energy expenditure. While thyroid hormone therapy helps, lifestyle interventions remain essential for effective weight management.<br />جامعة المستقبل الجامعة الاولى في العراق<br />قسم تقنيات المختبرات الطبية الاول في التصنيف الوطني العراقي