The thyroid and thymus glands are two separate and distinct glands in different locations with different functions.
The thyroid is a butterfly-shaped gland located in the front of your neck, below the larynx (voice box).
The thyroid gland secretes hormones that help control your body's metabolism and calcium balance. Low thyroid function can lead to many problems, including weight gain, hair loss, and fatigue.
The thymus gland is located in your upper chest under the sternum (breastbone).
The thymus gland is part of your immune system. It secretes hormones that enable T-Cells (disease-fighting cells) to function against disease-causing organisms. The thymus is most active in children and becomes less active with age.
According to The Women's Guide to Thyroid Health, low thyroid function can cause a reduction in the production of hormones by the thymus gland.