A trace element found in seawater and certain soils, iodine is essential in the production of hormones in the thyroid gland, and iodine deficiency can lead to thyroid issues. Here are a few signs you may be deficient in iodine: Swollen Neck A lack of iodine prevents the thyroid gland from producing enough thyroid hormones, leading to swelling of the gland in the neck. Fatigue Thyroid hormones help the body make energy; if these hormone levels are low, the body struggles to generate as much energy as usual, resulting in fatigue. Weight Gain Thyroid hormones control the body's metabolic rate, converting food into heat and energy; low levels of these hormones mean your body burns fewer calories while resting, resulting in weight gain. Hair Loss  Thyroid hormones regulate hair follicle growth. Low levels of these hormones due to an iodine deficiency can stop hair follicle regeneration, leading to hair loss over time. Dry Skin Those with an iodine deficiency may suffer from dry and flaky skin due to low levels of thyroid hormones, which aid the regeneration of skin cells.