Endocrinology is the science that studies the internal secretions produced by endocrine glands. Endocrine glands are spread throughout the body and secrete chemical messengers – i.e. hormones, in response to an internal or external stimulus. Hormones move through the bloodstream to different organs, where they exert a physiological control, even in low concentrations, managing diverse organic functions and maintaining homeostasis in the body.
Your dog’s endocrine system is made up of several organs called glands. These glands, located all over the body, create and release hormones. Hormones are chemicals that coordinate different functions in the dog’s body by carrying messages through the blood to their organs, skin, muscles and other tissues. These signals tell their body what to do and when to do it. The body evaluates and adjusts the level of each hormone by using a feedback system specifically for that particular hormone. Hormones operate to keep important factors such as body temperature and blood sugar (glucose) levels within a certain safe range at all times. Even hormones with opposite functions work together to keep the body functions in equilibrium.
Bodily functions that are controlled by the endocrine system include:
- Growth and development at all lifestages
- Reproductive functioning
- Heart rate
- Blood pressure
- Body temperature
The main glands that make up the endocrine system in a dog’s body are:
- Pituitary gland - The pituitary gland is located below the hypothalamus. The hormones it produces controls metabolism, growth, blood pressure and reproduction. It can also control the function of other endocrine glands. It makes hormones that control many other glands such as the thyroid gland, adrenal glands, ovaries and testicles.
- Hypothalamus – It produces multiple hormones that control the pituitary gland. The function of the hypothalamus is to maintain a dog’s internal balance, aka the homeostasis
- Thyroid and parathyroid glands – The thyroid gland, located at the base of neck, plays a major role in metabolism, growth and development of dogs. It produces hormones that regulate a dog’s metabolic rate, heart, muscle & digestive function, brain development & bone maintenance.
- Parathyroid glands – They are located next to the thyroid gland lobes in the neck. They regulate calcium in a dog’s body by discharging calcium from bones in the blood stream, and absorbing calcium from food through intestines.
- Adrenal glands – These are located on top of both kidneys. They regulate a dog’s metabolism, immune system, stress response etc
- Pancreas – Pancreas lies at the right side of a dog’s abdomen and produces enzymes that assist in digestion of food. It also produces hormones such as insulin, which regulates blood sugar or glucose metabolism.
- Ovaries (females only) and testes (males only), both release hormones as well as are responsible for reproduction
Endocrine system dysfunction:
Dogs are susceptible to the same diseases associated with the endocrine system as humans are. Among the conditions that can affect dogs are Diabetes, Hypothyroidism/Hyperthyroidism, Addison's disease, Cushing's disease, and other diseases that result when there is a dysfunction in glands of the endocrine system. Many things can affect how your dog’s body creates and releases hormones. Illness, stress and certain medications can lead to hormonal imbalance.
The following can be early signs of endocrine diseases in dogs:
- Increased or decreased appetite
- Increased or decreased thirst
- Increased or decreased weight
- Changes in the appearance of the skin and coat
- Increased urination
- Diarrhoea or vomiting
- Changes in mood/behavior
- Poor heat tolerance and excessive panting
- Lethargy and weakness
- Diabetes Mellitus – Diabetes Mellitus is the most common endocrine disease in dogs and is caused by failure of pancreas to regulate blood sugar. It is diagnosed in the presence of clinical signs related to elevated levels of blood glucose, and the inability to use glucose as energy source.
- Hypothyroidism – It is an underactive thyroid condition leading to a reduction in the dog’s metabolism. It happens when the thyroid glands fail to produce adequate amounts of the hormones thyroxine (T4) and triiodothyronine (T3). In dogs, hypothyroidism is usually caused by one of two diseases: lymphocytic thyroiditis or idiopathic thyroid gland atrophy. Lymphocytic thyroiditis disease is the most common cause of hypothyroidism and is thought to be immune-mediated. This means that the immune system decides that the thyroid is abnormal or foreign and attacks it. It is unclear why this occurs; however, it can be genetic or can be induced through an auto-immunity dysfunction.
- Cushing Disease – Cushing's disease (hyperadrenocorticism) is characterized by abdominal obesity, weight gain, fatigue, muscle atrophy and skin changes. It is a condition in which a dog’s adrenal glands overproduce cortisol.