The endocrine system is a connective network of glands that secrete and release hormones that help control many vital body functions, including the body's ability to change calories into energy that powers cells, tissues, and organs. Hormones are a class of signaling molecules in multicellular organisms often referred to as “messengers” because they originate in one organ and can travel throughout the body by blood and other body fluids to reach and mediate the function of other organs/tissues to regulate physiology/behavior.

Types of Hormones in the Human Body:

• Amino acid-derived hormones: Most of these hormones are neurotransmitters.
• Eicosanoids: Since these hormones are made from lipids, this is also known as lipid hormones.
• Peptides, polypeptides, and proteins: These hormones come in multiple forms that may differ in complexities. Hormones of this kind include TRH, vasopressin, insulin, growth hormone, and follicle-stimulating hormone.
• Steroid hormones: These hormones are made from cholesterol including sex hormones like testosterone, estradiol, and cortisol.
Hormones are produced by organs in the endocrine system and regulate a variety of activities. The hormone-producing glands are located throughout the body. The hormone producing glands include Pituitary, Pancreas, Thyroid, Thymus, Parathyroid, Adrenal, Hypothalamus, Pineal, Testes, and Ovaries.

Where the Deficiency Originates?

Endocrine disease results when the hormone-producing gland secretes too little or too much of endocrine hormone – often termed as hormonal imbalance. Endocrine disease is caused due to the development of lesions (for example, tumors or nodules) in the endocrine system. Hormones produced can be deficient or excess for the body and may not function properly, which may lead to various diseases such as:
• Hyperthyroidism/Hypothyroidism
• Cushing disease
• Addison disease
• Diabetes
• Disorders of puberty and reproductive function
• Age and related reproductive conditions, like menopause.
Growth hormone deficiency (GHD) is not usually present at birth; it may be caused by a tumor or nodule in the brain. These types of tumors are generally located at the site of the pituitary gland or the nearby hypothalamus region of the brain. In children and adults, infections, serious head injuries, and radiation treatments can also cause GHD.

The hyper- or hypo- secretion of endocrine hormone may be caused by:
• Inhibition or non-functioning of the endocrine feedback system
• Failure of a gland that stimulates another gland to release hormones (for example, any trouble in the hypothalamus can disrupt hormone production from the pituitary gland)
• The imbalance of hormone can also be due to a genetic disorder, for e.g., congenital hypothyroidism or multiple endocrine neoplasia (MEN)
• Infection
• Presence of tumor to an endocrine gland
Most endocrine nodules (lumps) and tumors are noncancerous. This usually does not spread to distant locations in the body. However, a tumor on the gland may interfere with the hormone production in the gland.

Growth hormone deficiency (GHD)/human growth hormone deficiency – a medical condition resulting from the absence/deficit of growth hormone (GH). Generally, the most noticeable symptom of the GHD deficiency is that an individual attains a short height. Hormone deficiencies include gland agenesis or destruction, mutations in genes for peptide hormones or synthetic enzymes for nonpeptide hormones, improper processing, regulatory defects leading to secretion failure, sequestering antibodies, and excessive metabolism.
The feedback system: The endocrine's feedback system helps control the balance of hormones in the bloodstream. If your body secretes a large or small amount of a certain hormone, the feedback system signals the gland or glands to fix the problem. A hormone imbalance may occur if this feedback system dysfunctions and does not maintain the perfect level of hormones in the bloodstream or if the body doesn't properly expel them out of the bloodstream.

Causes

The cause behind the hormonal disorders/deficiencies may include various factors such as mutations of specific genes (such as GHRHR, GH1), congenital diseases such as Prader-Willi syndrome, Turner syndrome, or short-stature homeobox gene deficiency, congenital malformations involving the pituitary gland (for e.g., septo-optic dysplasia, posterior pituitary ectopia), chronic kidney disease, the intracranial tumors in or near the sella turcica, especially craniopharyngioma, damage to the pituitary from brain radiation therapy (e.g. for leukemia or brain tumors), autoimmune inflammation, hemorrhagic or ischemic infarction from low blood pressure or hemorrhage pituitary apoplexy.

Various rare diseases that resemble growth hormone (GH) deficiency, including facial appearance, childhood growth failure, delayed bone age, and low levels of insulin-like growth factor-1 (IGF-1). However, GH testing elicits normal to high levels of GH in the blood, showing that the problem is not due to a deficiency of GH but rather due to a reduced sensitivity to its action.

Diagnosis

The diagnosis of GH deficiency in childhood is a multistep process, including clinical history examination with detailed auxology, pituitary imaging, and biochemical testing. Growth hormone deficiency results in abnormally slow growth and short stature with normal proportions. Diagnosis involves measurement of pituitary hormone levels and MRI or CT to detect structural pituitary anomalies or brain tumors. There is another accurate way to diagnose hormone deficiency – through a growth stimulation test.

Treatment

The treatment involves the development of Hormone-Behavior Relationships. TH deficiency in developing mammals, including humans, may lead to severe morphological and functional alterations of the CNS. The brain is an exceptionally important target of the TH, but its complexity has precluded an understanding of the mechanisms of action of THs. Most of these actions are exerted by the regulation of gene expression through the nuclear receptors. The common treatment for growth hormone deficiency among both adults and children is growth hormone therapy.