The thyroid affects nearly every system in the body, from the heart and digestion to mood, sleep and fertility; Israeli endocrinologists explain when to get tested, what TSH results mean and how thyroid disorders are treatedIt is small, quiet and usually unnoticed, until something goes wrong. The thyroid gland, located at the front of the neck, plays a central role in regulating metabolism. When it is not functioning properly, the effects can be felt across the body, including the heart, digestive system, weight, energy levels, mood, sleep, menstruation, fertility and pregnancy.Hypothyroidism and hyperthyroidism, meaning underactive and overactive thyroid function, are among the most common hormonal disorders, especially among women. Yet diagnosis is not always straightforward. Symptoms may be vague, develop slowly and be mistaken for fatigue, stress or aging.6 View gallery Thyroid dysfunction can affect energy levels, weight, heart health and mood(Photo: Shutterstock)To better understand when thyroid problems should be suspected, we spoke with Prof. Revital Dresner-Pollak, head of the Department of Endocrinology and Metabolism at Hadassah Medical Center, and Dr. Meir Frankel, director of the Endocrinology, Diabetes and Metabolism Unit at Shaare Zedek Medical Center.“Thyroid hormones act on every cell in the body,” Prof. Dresner-Pollak explains. “That is why when the gland is underactive or overactive, the effects are broad and can involve almost every system and organ.”The thyroid produces the hormones T4 and T3, but the gland itself is controlled by another hormone, TSH, which is secreted by the pituitary gland. “TSH is the hormone that tells the thyroid how much to work and how strongly,” Dr. Frankel says.When the thyroid does not produce enough hormones, TSH levels rise as the body tries to push the gland to work harder. When the thyroid is overactive and produces too many hormones, TSH levels fall. “Because of this relationship, TSH is the main marker we use to understand whether the thyroid is balanced,” Frankel says. “It is usually the first test we start with.”Prof. Revital Dresner-PollakPhoto: Hadassah Medical CenterDresner-Pollak says the control mechanism is important because even mild thyroid imbalance can produce a wide range of symptoms. “Since thyroid hormones affect every cell in the body, even a slight deviation in thyroid function can appear as many different symptoms, sometimes in several systems at once,” she says. “That is why doctors need to consider the broader clinical picture, rather than relying on a single blood-test result."One point many people do not know is that T4 is not the final active hormone. “T4 is not the final active hormone,” Dresner-Pollak says. “Inside the cells, it is converted into T3, and that is the hormone that actually affects metabolism and cellular function.”This helps explain why thyroid disorders can look so different from one person to another. Symptoms may involve the heart, digestion, muscles, nervous system, mood, reproductive system, fertility and pregnancy.“When the thyroid goes out of balance, there is not always one clear symptom,” she says. “Sometimes there is a combination of complaints from different systems that do not seem connected.”What is it?A condition in which the thyroid does not produce enough thyroid hormones, slowing the body’s metabolic activityCommon causesAutoimmune disease, Hashimoto’sThyroid removalRadioactive iodine treatmentNeck radiation for another conditionDiagnosisBlood tests: TSH, T4 and T3High TSH usually indicates hypothyroidismAdditional tests, antibodies, ultrasound or mapping, only when neededCommon symptomsFatigue and weaknessWeight gain or difficulty losing weightConstipationFeeling coldHair lossLow mood and difficulty concentratingMenstrual irregularitiesTreatmentHormone replacement therapy, usually a daily pillTreatment is not always needed in mild casesWhich blood tests can detect a thyroid disorder?