Endocrine System

The endocrine system is one of two communication systems that the body uses to convey information from one cell to another – the other is the nervous system. The endocrine system consists of all organs and tissues that secrete hormones.

The major organs include the thyroid and parathyroid glands, adrenal glands, pancreas, as well as the gonads. The hypothalamus and pituitary glands are also critical for integrating the actions of the nervous and endocrine systems.

The endocrine system in marine mammals is similar to that in other mammals. During necropsy, all major endocrine organs should be examined. In particular, examination of the adrenal gland can offer clues as to whether the animal had been experiencing chronic stress, such as from a long term illness. The adrenal gland is really two fused glands. The outer cortex secretes glucocorticoids and mineralcorticoids, hormones which help the body respond to stress and regulate salt and water balance.  The inner medulla of the adrenal gland on the other hand, secretes epinephrine and norepinephrine in response to stress and causes the body’s flight or fight response. While the effects of epinephrine and norepinephrine are immediate (helping you run away from the proverbial bear!), they wear off relatively faster than the effect of cortisol for example. When an animal experiences chronic stress, the cortex can become hypertrophied, leaving behind a clue that the animal was experiencing a chronic stress response prior to death.

 Detailed annotated images of the endocrine system in a harbor porpoise are shown below.  CLICK on an image to see an enlarged view.