The Two Types of Adrenal Insufficiency
There are two types of Adrenal Insufficiency, these are primary AI (Addison’s Disease) and secondary AI. Primary AI occurs when the actual adrenal glands are damaged and fail to work, whereas secondary AI is caused by a secondary issue such as the Pituitary gland in the brain not functioning properly and not sending the correct hormones to enable the adrenal glands to work. When the adrenals are not told by the pituitary to “make cortisol” the adrenals fail to function properly, hence the name secondary Adrenal Insufficiency.
What is the cause of Pituitary problems?
There are a number of reasons the pituitary can fail to function correctly. Firstly the Pituitary may not be receiving the correct signals from the hypothalamus, In this case the patient is labelled with Tertiary Adrenal Insufficiency. However if the original problem lies within the Pituitary gland this is usually due to some form of damage or disturbance taking place in this tiny area of the brain.
The pituitary can become damaged in a number of ways. For example through a trauma or accident which may have caused damage to the small pituitary gland or stalk or a pituitary tumour.
Pituitary tumours are generally not life threatening. There are two types of tumour, secretory and non secretory. Secretory secrete excess hormones and Non Secretory fail to secrete the hormone to the glands.
Someone who is Adrenally Insufficient due to a pituitary issue may have either damage to the gland or a non secreting tumour. This means the hormone ACTH will not be sent sufficiently to the adrenal glands to request the production of cortisol making one very unwell and resulting in daily cortisol replacement therapy.
As the pituitary is responsible for sending hormones to all the endocrine organs. People with pituitary problems may not suffer from Adrenal Insufficiency alone.
What hormones and functions are affected by a poor functioning Pituitary?
The pituitary gland also called the “master gland” control all parts of the endocrine system. Hormones are sent to the thyroid gland, adrenal glands, ovaries, and testes. The pituitary gland is tiny “about the size of a pea” and is divided into two segments the anterior and posterior lobes.
The hormones secreted from the anterior Pituitary are:
- Adrenocorticotropic hormone (ACTH): ACTH stimulates the adrenal glands to produce hormones.
- Follicle-stimulating hormone (FSH): FSH works with LH to ensure normal functioning of the ovaries and testes.
- Growth hormone (GH): GH is essential in early years to maintaining a healthy body composition and for growth in children. In adults, it aids healthy bone and muscle mass and affects fat distribution.
- Luteinizing hormone (LH): LH works with FSH to ensure normal functioning of the ovaries and testes.
- Prolactin: Prolactin stimulates breast milk production.
- Thyroid-stimulating hormone (TSH): TSH stimulates the thyroid gland to produce hormones.
The hormones secreted by the posterior Pituitary are:
- Anti-diuretic hormone (ADH): This hormone prompts the kidneys to increase water absorption in the blood.
- Oxytocin: Oxytocin is involved in a variety of processes, such as contracting the uterus during childbirth and stimulating breast milk production.
Why have a Brain MRI Scan of the Pituitary?
If someone is diagnosed with Adrenal Insufficiency, an Endocrinologist will need to work out whether the patient has Primary, Secondary or Tertiary AI. You can read about all the different test to work these out by clicking here. It is important for an Endocrinologist to rule out damage or a tumour to the pituitary as part of the diagnostic process of AI.
A Brain MRI of the Pituitary is generally a routine test to rule out the possibility of pituitary damage. If a problem is discovered, it is generally not life threatening and the Endocrinologist will be able to treat all hormones that are being affected, not just the lack of ACHT which resulted in low or no Cortisol and Secondary Adrenal Insufficiency.