Information About the Endocrine System, Syndromes and Lab Testing

 The endocrine system is a network that is made up of different glands throughout the human body. The endocrine system and the nervous system work together to regulate and control many of the internal functions of the body. The nervous system makes use of nerve impulses as its means for control; the endocrine system utilizes hormones, which are chemical messenger molecules. These hormones are created, stored, as well as secreted by an integrated network of different glands. When endocrine glands release different hormones into the blood, they will target specific organs, tissues, or cells. Every target will have dedicated receptors for that specific hormone, which can be explained as a key that fits into a lock.  

This network is made up of several parts. One of these is the hypothalamus, which is the endocrine gland situated in the brain. Another includes the pituitary gland, located in its own dedicated place inside of the sella turcica, just under the hypothalamus. The signals sent by the brain instruct the hypothalamus to create many types of hormones that either inhibit or stimulate the pituitary. These are the signals that make the pituitary either decrease or increase the hormones that it produces, followed by releasing them into the blood. Hormones that the pituitary releases in different amounts will travel through the blood to the endocrine glands. Some of these glands include the ovaries and testicles, adrenal, and thyroid glands. Many other tissues and organs in the body are also classified as hormone targets.  

Many of the endocrine glands are governed by specific feedback systems to prevent hormone imbalance. An example of this includes the hypothalamus that first stimulates the pituitary gland, followed by the adrenal gland to regulate the way it functions. The hypothalamus will first release CRH (corticotropin-releasing hormone), which stimulates the pituitary gland into releasing corticotropin (commonly known as an adrenocorticotrophic hormone or ACTH). ACTH then stimulates the adrenal gland into producing cortisol. When cortisol levels reach a specific threshold, the pituitary and the hypothalamus glands start to lower ACTH and CRH production, which creates a feedback loop that is negative.  

Certain hormones, like cortisol, have a monthly or a daily pattern or sequence of release. Levels of cortisol are usually higher in the mornings and lower in the evenings. The pituitary hormone levels of FSH (follicle-stimulating hormone) and LH (luteinizing hormone) decrease and increase in a regular pattern, which regulates the monthly menstrual cycles in women. Other types of hormones in the blood are typically present in far smaller quantities, will release in specific types of situations. An example of this is when adrenaline (epinephrine) is released from the adrenal glands as a direct response to a stressful situation.  

This gland network and the endocrine system are, in most cases, interdependent, which means any type of disorder which affects one of these glands can cause diseases that are linked to the other glands present in this system. For example, disorders that affect the hypothalamus might also impact on the pituitary gland along with the “downstream” targeted organs. The endocrine syndromes are often categorized by the affected gland.  

Primary disorders will affect one of the target organs, such as the adrenal or thyroid glands.  

Secondary disorders directly affect glands that perform the function of regulating the target organs. This is most commonly the pituitary gland.  

Tertiary disorders are linked to the hypothalamus.  

The Common Causes of Endocrine Syndromes 

Hormones influence multiple systems in the body, which includes the development of female and male characteristics, growth, fertility, digestion, stress response, glucose utilization, energy consumption, water/fluid balance, maintaining the correct blood pressure, and bone metabolism. When the glands are producing too little or too much of a hormone, it can affect these natural processes. This is a condition that is more commonly known as hormonal imbalances. These conditions also go by certain names, like Cushing syndrome (linked with excess cortisol), as they are associated with typical sets of complications and symptoms.  

Endocrine gland dysfunction might occur when the actual gland has a problem, an issue with the feedback-system, or/and when the target tissues are failing to respond to the hormone. When hormone production decreases, it can relate to infections when the immune system is damaged, trauma, crowding of hormone-producing cells caused by the presence of a tumor. Other causes also arise from a gene mutation (inherited) that affects the quality, quantity, or the overall structure of the hormone. When these glands are failing to release or produce enough hormone amounts to stimulate a targeted gland into releasing and producing its hormone, it might also lower production.  

An increase in the production of a hormone can be associated with an imbalance with the feedback system. An example of this is when the pituitary produces an excess amount of ACTH, which will disrupt and interfere with the feedback-system. An increase in production can also be linked to enlarged glands (hyperplasia) or tumors of the cells that produce these hormones. It can also occur when the tissue response is lacking, the use of certain types of medications, or inherited conditions.  

The endocrine tumors which are responsible for producing too many hormones are typically benign and small. Many of these are situated inside the gland that is affected, and that gland only produces one specific hormone type. These tumors rarely become cancerous. It is also very rare that an endocrine-disrupting tumor will be situated anywhere else inside the body. The tumor itself may be responsible for causing symptoms due to the hormone levels that it produces, as its growth will eventually crowd out and lower the production of any other hormone in the affected gland. This is also caused by the size of the tumor that puts pressure on the surrounding structures and nerves.  

Many of the endocrine conditions that are inherited are typically rare and are typically linked to dysfunctional or deficient production associated with one hormone. Or with the hormone production of glands, such as congenital hypothyroidism. There are, however, a few genetic syndromes or conditions that will affect several glands. The two that are identified to affect many of the endocrine glands include MEN-1 and MEN-2. This stands for Multiple Endocrine Neoplasia, Type 1 and Type 2.  

These are the conditions that relate to an alteration in genes. They also increase the likelihood that the affected person will develop a tumor or tumors in one or many of the endocrine glands in their body.  

Endocrine Disorders and Syndromes 

The common tests used to detect endocrine syndromes and disorders include: 


Adrenocorticotropic Hormone (ACTH) 

hCG Tumor Marker 





Antidiuretic Hormone (ADH) 


Thyroid-stimulating Hormone (TSH) 


Plasma Free Metanephrines 


Aldosterone and Renin 

Growth Hormone 


T3 (Free and Total) 

T4, Free 

Electrolytes and Anion Gap 

Follicle-stimulating Hormone (FSH) 

Sex Hormone Binding Globulin (SHBG) 

Luteinizing Hormone (LH) 


Insulin-like Growth Factor-1 (IGF-1) 

Urine Metanephrines 

Parathyroid Hormone (PTH)