The heaviest element that is considered essential to organisms as a trace element is iodine, which has an atomic number of 53. Iodine is an essential component of thyroid hormones, specifically triiodothyronine (T3) and thyroxine (T4). These hormones play a crucial role in regulating metabolism and growth in humans and other organisms.
While iodine is required in very small amounts by the body, its deficiency can lead to serious health issues, including goiter (enlarged thyroid gland) and developmental abnormalities. Adequate intake of iodine is especially important during pregnancy for proper fetal brain development.
It's worth noting that heavier elements beyond iodine, such as xenon (atomic number 54) and beyond, are not considered essential trace elements and do not play a known role in biological processes.