The use of punctuation in English can change from place to place and from time to time. Modern typography suggests that punctuation should only be used when there is a need. That results in less punctuation than was the case the early 20th century.
Hormone: A chemical substance produced in the body that controls and regulates the activity of certain cells or organs. Many hormones are secreted by special glands, such as thyroid hormone produced by the thyroid gland. Hormones are essential for every activity of life, including the processes of digestion, metabolism, growth, reproduction, and mood control. Many hormones, such as neurotransmitters, are active in more than one physical process.
Hormone is a chemical substance that is produced in one part of the body (by an endocrine gland) and is carried in the blood to other distant organs or tissues where it acts to modify their structure or function.