HOT FLASHES – Growth Hormone Disorders

HOT FLASHES – Growth Hormone Disorders
Elaine Cunanan, MD, FPCp, DPSEM

Growth hormone (GH) is a chemical produced by the pituitary gland, a tiny oval-shaped organ at the bottom of our brain. During childhood, it is important for linear growth or height increase. It is also important for muscle and bone development, and distribution of body fat throughout the body. In adulthood, it affects energy, muscle strength, bone health, and psychological well – being. Having either too much or too little growth hormone can cause health problems.

Growth hormone excess
How does it manifest?
Some individuals may have too much GH. This leads to gigantism, or extremely tall stature, if it occurs during childhood. In adults, excessive GH leads to acromegaly, which is the overgrowth .of body tissues with subsequent coarsening of facial features and increase in hand and feet sizes. Height doesn’t increase anymore since vertical growth stops when the long bones cease to lengthen with closure of bone growth centers during puberty.

GH excess is usually caused by a noncancerous tumor of the pituitary gland.

Gigantism and acromegaly are rare diseases. Only three to four cases are diagnosed per million people each year.

The features associated with GH excess develop very gradually and may not even be recognized for many years.

Other manifestations that may be associated with GH excess include:
• Headaches
• Numbness or burning sensation of the hands or feet due to carpal tunnel syndrome
• Diabetes mellitus
• Heart attack, heart failure, or enlarged heart
• High blood pressure
• Goiter (enlarged thyroid gland)
• Sleep apnea
• Tiredness
• Menstrual disorders (irregular bleeding; absence of periods)
• Decreased libido (low sex drive)
• Vision problems (tunnel vision; vision loss)
• Psychological problems (depression; anxiety)

Persons with untreated growth hormone excess have a mortality rate that is two to three times higher than the general population. This is mainly due to cardiovascular and respiratory complications.

How is it diagnosed?
Growth hormone stimulates the production of another substance called insulin-like growth factor-1 (IGF-1) by the liver and other body tissues. Excess GH therefore leads to excess IGF-1. Measuring the level of IGF-1 in the blood is a good test to confirm GH excess. We can also measure blood GH level one to two hours after giving oral glucose. If either IGF-1 or blood GH is elevated, magnetic resonance imaging (MRI) scan of the pituitary gland is requested to determine whether a tumor is the cause of the excess hormone secretion.

How is it treated?
Once GH excess is confirmed and a pituitary tumor is seen on MRI, surgery to remove the tumor is the treatment of choice. If surgery does not normalize the GH level (eg. in large tumors), or if a patient cannot undergo surgery, other therapies include medications and irradiation of the pituitary gland. Radiation is considered a last resort in children with GH excess, because of possible effects on the developing brain.

The following drugs may be used for treatment of GH excess – somatostatin analogues, GH receptor antagonists (not available in our country), and dopamine agonists. These medications mainly work to reduce levels of GH or IGF-1.

Treated patients need to be monitored to make sure that GH excess does not return. Patients should also be monitored for medical problems associated with GH excess, which include heart disease, hypertension, colon polyps, and diabetes mellitus.

Loss of other hormones produced by the pituitary gland can result from tumor impingement. It can also be a complication of surgery or radiation therapy. Patients, therefore, need to be watched for signs of hypopituitarism caused by low levels of pituitary hormones. If this occurs, the patient will require appropriate hormone replacement therapy.

Growth hormone deficiency
How does it manifest?
Growth hormone deficiency (GHD) is the condition of having too little GH. A child can be born with GHD due to problems in the development of the pituitary gland and hypothalamus. The condition may also arise because of damage to the hypothalamus or pituitary gland as a child or adult because of a tumor, an infection, or radiation to the brain. Some may have GHD due to still undefined cause (idiopathic).

Children with GHD have persistently below average growth rate. They may have extra fat in the abdomen and face. As adolescents, they may show signs of delayed sexual maturity.

Possible symptoms in adults with GHD include:
• Increased body fat (particularly at the waist)
• Decreased muscle and bone mass
• Thinning skin with fine wrinkles
• Poor sweating or impaired temperature regulation
• Reduced strength and endurance
• Low energy level
• Decreased well-being (moodiness, mild depression)
• Loss of interest in sex
• Poor sleep
• High LDL (“bad”) cholesterol

How is it diagnosed?
There is currently no “gold standard”

Children with GHD have persistently below average growth rate. They may have extra fat in the abdomen and face. As adolescents, they may show signs of delayed sexual maturity.

test for the diagnosis of GHD. Because the pituitary gland secretes GH in bursts throughout the day, random measurements of GH levels in the blood are not useful. GH stimulation tests using agents that stimulate GH secretion (eg insulin, glucagon or arginine) are commonly used. Low blood IGF-1 level may support GHD.

How is it treated?
Treatment involves giving GH (usually comes in pens) as a daily injection under the skin.

Children should be evaluated every three to six months to monitor height and rate of growth. When children with GHD reach late teenage years, tests should be done to see if they still need GH therapy until adulthood.

Side effects of growth hormone therapy in childhood are very rare. The most worrisome are increased intracranial pressure and a hip disorder called slipped capital femoral epiphysis.
Currently, there are differences in opinion about when to give growth hormone to adults with GHD. Experts generally recommend GH replacement for adults with severe clinical manifestations and clear evidence of GHD due to hypothalamic-pituitary disease.

Adults tend to experience more side effects than children. Most common side effects are peripheral edema (leg swelling), painful joints, carpal tunnel syndrome, numbness, and “unmasking” or worsening of diabetes.

GH therapy is not advisable for patients with active cancer because of theoretical possibility that GH could stimulate tumor growth.

GH excess and GHD are best evaluated and treated by endocrinologists medical specialists in hormone-related conditions. Because the diagnosis and treatment of such disorders require special expertise, patients suspected to have GH abnormalities should ideally be referred to an endocrinologist.

References:
The Hormone Foundation: http://www.hormone.org/
Uptodate: httpwww.uptodate.com/

 

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