The Child with Endocrine Dysfunction



The Child with Endocrine Dysfunction


Elizabeth Record and Linda K. Ballard



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evolve.elsevier.com/wong/essentials





The Endocrine System


The endocrine system consists of three components: (1) the cells, which send chemical messages by means of hormones; (2) the target cells, or end organs, which receive the chemical messages; and (3) the environment through which the chemicals are transported (blood, lymph, extracellular fluids) from the sites of synthesis to the sites of cellular action. The endocrine system controls or regulates metabolic processes governing energy production, growth, fluid and electrolyte balance, response to stress, and sexual reproduction (Baxter and Ribeiro, 2004). The endocrine glands, which are distributed throughout the body, are listed in Table 29-1; also listed are several additional structures sometimes considered endocrine glands, although they are not usually included. The pathophysiology review in Figure 29-1 provides a summary of the principle pituitary hormones and their target organs.



TABLE 29-1


Hormones and Their Function















































































































































HORMONE EFFECT HYPOFUNCTION HYPERFUNCTION
Adenohypophysis (Anterior Pituitary)*
STH or GH (somatotropin)
Target tissue—Bones



Thyrotropin (TSH)
Target tissue—Thyroid gland



ACTH
Target tissue—Adrenal cortex



Gonadotropins
Target tissue—Gonads



FSH
Target tissue—Ovaries, testes



Luteinizing hormone (LH)
Target tissue—Ovaries, testes



Prolactin (luteotropic hormone)
Target tissue—Ovaries, breasts



MSH
Target tissue —Skin



Neurohypophysis (Posterior Pituitary)
ADH (vasopressin)
Target tissue—Renal tubules



Oxytocin
Target tissue—Uterus, breasts

   
Thyroid
THs—T4 and T3


Thyrocalcitonin
   
Parathyroid Glands
PTH


Adrenal Cortex
Mineralocorticoids
 Aldosterone



Sex hormones—Androgens, estrogens, progesterone


Glucocorticoids
 Cortisol (hydrocortisone and compound F)
 Corticosterone (compound B)



Adrenal Medulla
Epinephrine (adrenaline), norepinephrine (noradrenaline)
 
Islets of Langerhans of Pancreas
Insulin (β cells)


Glucagon (α cells)
 
Somatostatin (δ cells)
   
Ovaries
Estrogen


Progesterone
   
Testes
Testosterone




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ACTH, Adrenocorticotropic hormone; ADH, antidiuretic hormone; DKA, diabetic ketoacidosis; DM, diabetes mellitus; FSH, follicle-stimulating hormone; GH, growth hormone; GI, gastrointestinal; MSH, melanocyte-stimulating hormone; PTH, parathyroid hormone; SIADH, syndrome of inappropriate antidiuretic hormone secretion; STH, somatotropin hormone; T3, triiodothyronine; T4, thyroxine; TH, thyroid hormone; TSH, thyroid-stimulating hormone.


*For each anterior pituitary hormone there is a corresponding hypothalamic-releasing factor. A deficiency in these factors caused by inhibiting anterior pituitary hormone synthesis produces the same effects. (See text for more detailed information.)


In males, LH is sometimes known as interstitial cell–stimulating hormone (ICSH).




Hormones


A hormone is a complex chemical substance produced and secreted into body fluids by a cell or group of cells that exerts a physiologic controlling effect on other cells (Kliegman, Stanton, St. Geme, and others, 2011). These effects may be local or distant and may affect either most cells of the body or specific “target” tissues. Hormones are released by the endocrine glands into the bloodstream, and production is regulated by a feedback mechanism (see Table 29-1). The master gland of the endocrine system is the anterior pituitary, which is in turn controlled by the hypothalamus. Some hormones, such as insulin, are regulated by other mechanisms.



Disorders of Pituitary Function


The pituitary gland is divided into two lobes, the anterior and the posterior lobes. Each lobe is responsible for different hormones. Disorders of the anterior pituitary hormones may be attributable to organic defects or have an idiopathic etiology and may occur as a single hormonal problem or in combination with other hormonal disorders. The clinical manifestations depend on the hormones involved and the age of onset. Panhypopituitarism is often defined clinically as the loss of all anterior pituitary hormones, leaving only posterior function intact (Toogood and Stewart, 2008).




Hypopituitarism


Hypopituitarism is diminished or deficient secretion of pituitary hormones. The consequences of the condition depend on the degree of dysfunction and can lead to gonadotropin deficiency with absence or regression of secondary sex characteristics; growth hormone (GH) deficiency, in which children display retarded somatic growth; thyroid-stimulating hormone (TSH) deficiency, which produces hypothyroidism; and corticotropin deficiency, which results in manifestations of adrenal hypofunction. Hypopituitarism can result from any of the conditions listed in Box 29-1. The most common organic cause of pituitary undersecretion is tumors in the pituitary or hypothalamic region, especially the craniopharyngiomas. Congenital hypopituitarism can be seen in newborn infants, often as a result of birth trauma. Symptoms of hypoglycemia and seizure activity often manifest within the first 24 hours after birth (Toogood and Stewart, 2008).



Idiopathic hypopituitarism, or idiopathic pituitary growth failure, is usually related to GH deficiency, which inhibits somatic growth in all cells of the body (Miller and Zimmerman, 2004). Growth failure is defined as an absolute height of less than −2 standard deviation (SD) for age or a linear growth velocity consistently less than −1 SD for age. When this occurs without the presence of hypothyroidism, systemic disease, or malnutrition, then an abnormality of the GH–insulin-like growth factor (IGF-I) axis should be considered (Richmond and Rogol, 2008). Not all children with short stature have GH deficiency. In most instances, the cause is either familial short stature or constitutional growth delay. Familial short stature refers to otherwise healthy children who have ancestors with adult height in the lower percentiles. Constitutional growth delay refers to individuals (usually boys) with delayed linear growth, generally beginning as a toddler, and skeletal and sexual maturation that is behind that of age mates (Halac and Zimmerman, 2004; Miller and Zimmerman, 2004). Typically, these children will reach normal adult height. Often there is a history of a similar pattern of growth in one of the child’s parents or other family members. The untreated child will proceed through normal changes as expected on the basis of bone age. Although treatment with GH is not usually indicated, its use has become controversial, especially in relation to parental and child requests for treatment to accelerate growth.




Diagnostic Evaluation


Only a small number of children with delayed growth or short stature have hypopituitary dwarfism. In the majority of instances, the cause is constitutional delay. Diagnostic evaluation is aimed at isolating organic causes, which, in addition to GH deficiency, may include hypothyroidism, oversecretion of cortisol, gonadal aplasia, chronic illness, nutritional inadequacy, Russell-Silver dwarfism, or hypochondroplasia.


A complete diagnostic evaluation should include a family history, a history of the child’s growth patterns and previous health status, physical examination, psychosocial evaluation, radiographic surveys, and endocrine studies. Accurate measurement of height (using a calibrated stadiometer) and weight and comparison with standard growth charts are essential. Multiple height measures reflect a more accurate assessment of abnormal growth patterns (Box 29-2) (Hall, 2000). Parental height and familial patterns of growth are important clues to diagnosis.



Box 29-2


Evaluating the Growth Curve




Ensure reliability of measurements. Accurately obtain and plot height and weight measurements.


Determine absolute height. The child’s absolute height bears some relationship to the likelihood of a pathologic condition. However, the majority of children who have a height below the lowest percentile (either the third or fifth percentile on the height curve) do not have a pathologic growth problem.


Assess height velocity. The most important aspect of a growth evaluation is the observation of a child’s height over time, or height velocity. Accurate determination of height velocity requires at least 4 and preferably 6 months of observation. A substantial deceleration in height velocity (crossing several percentiles) between 3 and 12 or 13 years of age indicates a pathologic condition until proven otherwise.


Determine weight-to-height relationship. Determination of the weight-to-height ratio has some diagnostic value in ascertaining the cause of growth retardation in a short child.


Project target height. The height of a child can be judged inappropriately short only in the context of his or her genetic potential. Determine the target height of the child with the formula:



Modified from Vogiatzi MG, Copeland KC: The short child, Pediatr Rev 19(3):92–99, 1998.


A skeletal survey in children younger than 3 years of age and radiographic examination of the hand–wrist for centers of ossification (bone age) (Box 29-3) in older children are important in evaluating growth.



Definitive diagnosis is based on absent or subnormal reserves of pituitary GH. Because GH levels are variable in children, GH stimulation testing is usually required for diagnosis. Initial assessment of the serum IGF-I and IGF binding protein 3 (IGFBP3) indicates a need for further evaluation of GH dysfunction if levels are less than −1 SD below the mean for age. It is recommended that GH stimulation tests be reserved for children with low serum IGF-I and IGFBP3 levels and poor growth who do not have other causes for short stature (Richmond and Rogol, 2008). GH stimulation testing involves the use of pharmacologic agents such as levodopa, clonidine, arginine, insulin, propranolol, or glucagon to provoke the release of GH (Kliegman, Stanton, St. Geme, and others, 2011). Children with poor linear growth, delayed bone age, and abnormal GH stimulation tests are considered GH deficient.



Therapeutic Management


Treatment of GH deficiency caused by organic lesions is directed toward correction of the underlying disease process (e.g., surgical removal or irradiation of a tumor). The definitive treatment of GH deficiency is replacement of GH, which is successful in 80% of affected children. Biosynthetic GH is administered subcutaneously on a daily basis. Growth velocity increases in the first year and then declines in subsequent years. Final height is likely to remain less than normal (Bryant, Baxter, Cave, and others, 2007), and early diagnosis and intervention are essential (Leschek, Rose, Yanovski, and others, 2004).


The decision to stop GH therapy is made jointly by the child, family, and health care team. Growth rates of less than 1 inch per year and a bone age of more than 14 years in girls and more than 16 years in boys are often used as criteria to stop GH therapy (Kliegman, Stanton, St. Geme, and others, 2011). Children with other hormone deficiencies require replacement therapy to correct the specific disorders.



Nursing Care Management


The principal nursing consideration is identifying children with growth problems. Even though the majority of growth problems are not a result of organic causes, any delay in normal growth and sexual development poses special emotional adjustments for these children.


The nurse may be a key person in helping establish a diagnosis. For example, if serial height and weight records are not available, the nurse can question parents about the child’s growth compared with that of siblings, peers, or relatives. Preparation of the child and family for diagnostic testing is especially important if a number of tests are being performed, and the child requires particular attention during provocative testing. Blood samples are usually taken every 30 minutes for a 3-hour period. Children also have difficulty overcoming hypoglycemia generated by tests with insulin, so they must be observed carefully for signs of hypoglycemia, but those receiving glucagon are at risk of nausea and vomiting. Clonidine may cause hypotension, requiring administration of intravenous (IV) fluids.



Child and Family Support

Children undergoing hormone replacement require additional support. The nurse should provide education for patient self-management during the school-age years. Nursing functions include family education concerning medication preparation and storage, injection sites, injection technique, and syringe disposal (see Chapter 22). Administration of GH is facilitated by family routines that include a specific time of day for the injection. Younger children may enjoy using a calendar and colorful stickers to designate received injections.



Even when hormone replacement is successful, these children attain their eventual adult height at a slower rate than their peers; therefore, they need assistance in setting realistic expectations regarding improvement. Because these children appear younger than their chronologic age, others frequently relate to them in infantile or childish ways. Parents and teachers benefit from guidance directed toward setting realistic expectations for the child based on age and abilities. For example, in the home, such children should have the same age-appropriate responsibilities as their siblings. As they approach adolescence, they should be encouraged to participate in group activities with peers. If abilities and strengths are emphasized rather than physical size, such children are more likely to develop a positive self-image.


Professionals and families can find resources for research, education, support, and advocacy from the Human Growth Foundation.* The treatment is expensive, but the cost is often partially covered by insurance if the child has a documented deficiency. Children with panhypopituitarism should be advised to wear medical identification at all times.



Pituitary Hyperfunction


Excess GH before closure of the epiphyseal shafts results in proportional overgrowth of the long bones until the individual reaches a height of 2.4 m (8 ft) or more. Vertical growth is accompanied by rapid and increased development of muscles and viscera. Weight is increased but is usually in proportion to height. Proportional enlargement of head circumference also occurs and may result in delayed closure of the fontanels in young children. Children with a pituitary-secreting tumor may also demonstrate signs of increasing intracranial pressure, especially headache.


If oversecretion of GH occurs after epiphyseal closure, growth is in the transverse direction, producing a condition known as acromegaly. Typical facial features include overgrowth of the head, lips, nose, tongue, jaw, and paranasal and mastoid sinuses; separation and malocclusion of the teeth in the enlarged jaw; disproportion of the face to the cerebral division of the skull; increased facial hair; thickened, deeply creased skin; and an increased tendency toward hyperglycemia and diabetes mellitus (DM). Acromegaly can develop slowly, leading to delays in diagnosis and treatment.






Precocious Puberty


Manifestations of sexual development before age 9 years in boys or age 8 years in girls have traditionally been considered precocious development, and these children were recommended for further evaluation (Kempers and Otten, 2002; Midyett, Moore, and Jacobson, 2003). Recent examination of the age limit for defining when puberty is precocious reveals that the onset of puberty in girls is occurring earlier than previous studies have documented (Biro, Huang, Crawford, and others, 2006; Slyper, 2006). The mean onset of puberty was 10.2 years in white girls and 9.6 years in African-American girls. Based on these findings, precocious puberty evaluation for a pathologic cause should be performed for white girls younger than 7 years of age or for African-American girls younger than 6 years of age. No change in the guidelines for evaluation of precocious puberty in boys is recommended. However, recent data suggest that boys may be beginning maturation earlier as well (Herman-Giddens, 2006; Slyper, 2006).


Normally, the hypothalamic-releasing factors stimulate secretion of the gonadotropic hormones from the anterior pituitary at the time of puberty. In boys, interstitial cell–stimulating hormone stimulates Leydig cells of the testes to secrete testosterone; in girls, follicle-stimulating hormone (FSH) and luteinizing hormone stimulate the ovarian follicles to secrete estrogens (Nebesio and Eugster, 2007). This sequence of events is known as the hypothalamic–pituitary–gonadal axis. If for some reason the cycle undergoes premature activation, the child will display evidence of advanced or precocious puberty. Causes of precocious puberty are found in Box 29-4.


Jan 16, 2017 | Posted by in NURSING | Comments Off on The Child with Endocrine Dysfunction
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