Introduction:
The growth hormone is a vital hormone produced and secreted by the anterior pituitary gland. It is responsible for regulating growth and development in children, maintaining a normal structure, and regulating blood sugar levels in adults. An insufficiency or complete absence of growth hormone can cause various physical problems, including short stature, retarded growth, retarded bone maturation, delayed closure of skull sutures, etc. This growth hormone deficiency can be congenital, acquired, or idiopathic.
What Is the Growth Hormone?
Hormones are signaling molecules of the body that are produced and released by the various endocrine glands. Growth hormone is a vital hormone secreted by the anterior pituitary gland along with other hormones. The pituitary gland is a tiny endocrine gland located at the base of the skull. It is responsible for controlling major functions of the body along with controlling various other endocrine glands. As suggested by its name, the growth hormone’s key function is regulating growth and development in children and adolescents. The anterior pituitary gland releases growth hormone into the blood, from where it reaches various receptors and acts accordingly. Growth hormone promotes growth in children by acting on many different body regions. Growth hormone has little effect on height until the growth plates in the bones (epiphyses) have fused. It does not cause growth in adults but promotes the maintenance of normal body structure and metabolism, especially regulating blood sugar levels.
What Are the Subdivisions of Growth Hormone Deficiency?
Based on the cause and the time of onset, growth hormone deficiency can be of three types:
-
Congenital Growth Hormone Deficiency: This is a condition in which the baby is born with a growth hormone insufficiency. Until the infant is 6 to 12 months old, the child will appear to grow normally. This disease is frequently accompanied by an inborn deficiency of other hormones. Genetic mutations or anatomical problems in the brain cause congenital isolated growth hormone insufficiency.
-
Acquired Growth Hormone Deficiency: Acquired growth hormone deficiency occurs when the body suddenly stops producing growth hormones. This condition is non-congenital and can affect anyone at any age in adulthood. Trauma, infection, radiation therapy, or pituitary gland tumor in the brain can cause acquired growth hormone insufficiency.
-
Idiopathic Growth Hormone Deficiency: Growth hormone deficiency without any known cause is called idiopathic isolated growth hormone deficiency.
What Is Isolated Growth Hormone Deficiency?
Isolated growth hormone deficiency is an uncommon condition in which the anterior pituitary gland fails to produce enough growth hormone. As a result, there is a lack or absence of growth hormones in the body. Growth hormone is required for the normal development of the bones and tissues of the body. Individuals with isolated growth hormone deficiency frequently fail to grow at the average expected rate because they lack enough of this hormone. As a result, it causes growth retardation, small height, and delayed bone maturation that does not coincide with the child's chronological age. Growth hormone deficiency in adults is most commonly caused by a pituitary tumor or a brain injury, but it can also be sporadic or idiopathic (no known cause). Reduced energy levels, altered body composition, osteoporosis (low bone mineral density), reduced muscle strength, and other symptoms are signs of isolated growth hormone deficiency in adults. Isolated growth hormone deficiency is a rare condition affecting 1 in every 4,000 to 10,000 people globally.
What Are the Types of Isolated Growth Hormone Deficiency?
Based on their severity, involved gene, and nature of inheritance, there are four types of isolated growth hormones deficiency:
Type IA: This is the most severe type of isolated growth hormone deficiency, and growth failure is noticeable even in infancy.
Type IB: Individuals affected by this type of isolated growth hormone deficiency produce a very small amount of growth hormone. Therefore, the growth failure is not as severe as type 1B. However, the symptoms of this type are visible in mid-childhood.
Type II: Individuals with isolated growth hormone deficiency type II possess low growth hormone levels and varying degrees of short stature. These people's growth failure usually shows itself in their early to mid-adolescents. The pituitary gland is thought to be underdeveloped in approximately half of those with type II diabetes.
Type III: In type III isolated growth hormone deficiency, in addition to the symptoms of type II, the affected individual shows weak immunity and susceptibility to contracting infections.
What Causes Isolated Growth Hormone Deficiency?
-
Congenital isolated growth hormone deficiency occurs to genetic mutation or variation in gene pattern.
-
Type IA is an autosomal recessive disorder that causes fetal growth retardation. Autosomal recessive disorder means the child inherits one copy of the mutated gene from each parent. An inherited disorder is a disorder that is passed down from parents to their children.
-
Type IB is also similar to type IA and is autosomal recessive in the inheritance pattern.
-
Type II is inherited in an autosomal dominant pattern (only one copy of the mutated gene from one of the parents is required).
-
Type III is an X-linked condition, which means traits are influenced by X-chromosome genes.
What Are the Symptoms of Isolated Growth Hormone Deficiency?
The various signs and symptoms of isolated growth hormone deficiency are:
-
Normal size at birth except in type IA where the child looks smaller than average newborns.
-
Some children have low blood sugar levels.
-
Males may have a small penis.
-
Delayed rate of facial bone development.
-
Delayed eruption of teeth.
-
Retarded or delayed long bone lengthening.
-
Fine hair.
-
Poor nail growth.
-
High-pitched voiced.
-
Truncal obesity (excessive abdominal fat).
-
Closure of skull sutures is delayed.
-
An individual who develops growth hormone deficiency in adulthood has more generalized signs and symptoms. They may notice an increased abdominal and visceral fat mass and loss of muscle mass. Tiredness, anxiety, and depression are all typical symptoms. LDL (low-density lipoprotein) cholesterol and triglyceride levels are impacted, resulting in a rise in LDL cholesterol and triglyceride levels.
How to Diagnose Isolated Growth Hormone Deficiency?
The diagnosis of isolated growth hormone deficiency is made in the following ways:
-
A detailed medical and familial history, along with a thorough physical examination, is required for the diagnosis of isolated growth hormone deficiency.
-
The essential criteria for diagnosing growth hormone deficiency in children are growth increments. Normal levels of growth usually follow a pattern; a ten percent decrease in the growth rate can lead to reduced growth. Therefore, a significant decline in the growth chart is noticed. When this is established, the child should then be tested for the levels of growth hormone.
-
Insulin, arginine, clonidine, and l-dopa are some of the agents that can be used to test for growth hormone deficiency. These tests induce the pituitary to release growth hormone, allowing blood samples to be collected and examined for growth hormone levels at predetermined intervals.
-
Other hormone imbalances that may cause short stature are also frequently tested by doctors to rule out other possible causes of low stature. Tests such as freeT4, TSH (thyroid stimulating hormone), cortisol, celiac antibodies, and others are performed.
-
Growth hormone deficiency can also be determined by monitoring IGF-1 (insulin-like growth factor-1), a protein produced principally by the liver but also detected in other organs and tissues. This protein is secreted in response to growth hormone stimulation.
How Is Isolated Growth Hormone Deficiency Treated?
The treatment modalities of isolated growth hormone deficiency include:
-
To maximize development potential, children with growth hormone deficiency should be treated with recombinant human growth hormone once the disease is diagnosed and confirmed.
-
The dose is steadily increased until it reaches its maximum during puberty, and then it is stopped at or near the end of skeletal development or maturation.
-
If the patient reaches adulthood, they may need to be retested to see if growth hormone therapy is still required.
-
Somatropin, Humatrope, Genotropin, Saizen, Norditropin, Tev-Tropin, and Omnitrope have all been approved by the FDA (Food and Drug Administration) for the treatment of growth hormone insufficiency.
Conclusion:
Isolated growth hormone deficiency is a rare yet serious condition. Although it is generally not life-threatening and does not affect the child’s intellect, it causes various physical abnormalities that not only adversely affect physical capabilities but also put the child under a great amount of mental stress. However, if the condition is diagnosed early and treated with the correct medication and hormone therapy, it can be managed with an excellent prognosis.
