NCLEX: Endocrine disorders

Endocrine disorders: A look at endocrine disorders

Focus topic: Endocrine disorders

Endocrine disorders alter a patient’s health and self-image. These disorders may affect the patient’s growth and development, reproductive system, energy level, metabolic rate, or ability to adapt to stress. Some disorders, such as Cushing’s syndrome and goiter, profoundly alter the body. Others, such as diabetes mellitus, require the patient to follow a stringent drug regimen and meal plan.

Endocrine disorders: Anatomy and physiology

Focus topic: Endocrine disorders

The endocrine system consists of three major components:

  • glands, which are specialized cell clusters or organs
  • hormones, which are chemical substances secreted by glands in response to stimulation
  • receptors, which are protein molecules that trigger specific physiologic changes in a target cell in response to hormonal stimulation.

Endocrine disorders: Glands

Focus topic: Endocrine disorders

The major glands of the endocrine system are:
• pituitary gland
• thyroid gland
• parathyroid glands
• adrenal glands
• pancreas
• thymus
• pineal gland
• gonads (ovaries and testes).

Pituitary gland
The pea-sized pituitary gland, located on the inferior aspect of the brain, is called the “master gland” because it regulates many key processes. It has two lobes: the posterior lobe, which stores and releases oxytocin and antidiuretic hormone produced by the hypothalamus, and the anterior lobe, which produces at least six hormones.

  • growth hormone (GH), or somatotropin
  • thyroid-stimulating hormone (TSH), or thyrotropin
  • corticotropin
  • follicle-stimulating hormone (FSH)
  • luteinizing hormone (LH)
  • prolactin.

Thyroid gland

The thyroid gland lies directly below the larynx, partially in front of the trachea. Its two lateral lobes — one on either side of the trachea — join with a narrow tissue bridge, called the isthmus, to give the gland its butterfly shape. The two lobes of the thyroid function as one unit to produce two hormones:
• Triiodothyronine (T3) and thyroxine (T4), collectively referred to as thyroid hormone, are the body’s major metabolic hormones.
• Calcitonin maintains the blood calcium level by inhibiting the release of calcium from bone.

Parathyroid glands
Four parathyroid glands lie embedded on the posterior surface of the thyroid, one in each corner. Like the thyroid lobes, the para thyroid glands work together as a single gland, producing para thyroid hormone (PTH), which helps regulate the blood’s calcium balance.

Endocrine disorders

Adrenal glands
The two adrenal glands sit atop the two kidneys. Each gland contains two distinct structures — the adrenal cortex and the adrenal medulla — that function as separate endocrine glands. The adrenal medulla, the inner portion, produces catecholamines. Because catecholamines play an important role in the autonomic nervous system, the adrenal medulla is considered a neuroendocrine structure.

Zoning in on the outer layer

Focus topic: Endocrine disorders

The adrenal cortex is the large outer layer. It has three zones, or cell layers:
• The zona glomerulosa, the outermost zone, produces mineralocorticoids, primarily aldosterone.
• The zona fasciculata, the middle and largest zone, produces the glucocorticoids cortisol (hydrocortisone), cortisone, and corticosterone as well as small amounts of the sex hormones androgen and estrogen.
• The zona reticularis, the innermost zone, produces mainly glucocorticoids and some sex hormones.

Pancreas
The pancreas, nestled in the curve of the duodenum, stretches horizontally behind the stomach and extends to the spleen. The islets of Langerhans, which perform the endocrine function of this gland, contain alpha, beta, and delta cells. Alpha cells produce glucagon; beta cells, insulin; and delta cells, somatostatin.

Thymus
The thymus is located below the sternum and contains lymphatic tissue. Although this gland produces the hormones thymosin and thymopoietin, its major role seems related to the immune system; it produces T cells, which are important in cell-mediated immu nity.

Pineal gland
The tiny pineal gland lies at the back of the third ventricle of the brain. It produces the hormone melatonin, which may play a role in the neuroendocrine reproductive axis as well as other widespread actions.

Gonads
The gonads include the ovaries (in females) and the testes (in males). The ovaries promote development and maintenance of the female sex characteristics, regulate the menstrual cycle, maintain the uterus for pregnancy and, along with other hormones, prepare the mammary glands for lactation. The testes produce spermatozoa and the male sex hormone testosterone. Testosterone stimulates and maintains male sex characteristics.

Endocrine disorders: Hormones

Focus topic: Endocrine disorders

Structurally, hormones can be classified into three types:
amines
polypeptides
steroids.

Amenable amines

Focus topic: Endocrine disorders

Amines are derived from tyrosine, an essential amino acid found in most proteins. They include the thyroid hormones (T3 and T4) and the catecholamines (epinephrine, norepinephrine, and dopamine).

Poly want a peptide?

Focus topic: Endocrine disorders

Polypeptides are protein compounds made of many amino acids that are connected by peptide bonds. They include anterior pituitary hormones (GH, TSH, corticotropin, FSH, LH, interstitial cell stimulating hormone, and prolactin), posterior pituitary hormones (antidiuretic hormone [ADH] and oxytocin), PTH, and pancreatic hormones (insulin and glucagon).

Steroids: So sexy

Focus topic: Endocrine disorders

Steroids, derived from cholesterol, include the adrenocortical hormones secreted by the adrenal cortex (aldosterone and cortisol) and the sex hormones (estrogen and progesterone in females and testosterone in males) secreted by the gonads.

Hormonal release and transport
Although all hormone release results from endocrine gland stimulation, their release patterns vary greatly.
• Corticotropin (secreted by the anterior pituitary) and cortisol (secreted by the adrenal cortex) are released in irregular spurts in response to body rhythm cycles, with levels peaking in the early morning.
• Secretion of PTH (by the parathyroid gland) and prolactin (by the anterior pituitary) occurs fairly evenly throughout the day.
• Secretion of insulin by the pancreas has both steady and sporadic release patterns.

Hormonal action
When a hormone reaches its target site, it binds to a specific receptor on the cell membrane or within the cell. Polypeptides and some amines bind to membrane receptor sites. The smaller, more lipid-soluble steroids and thyroid hormones diffuse through the cell membrane and bind to intracellular receptors.

Right on target!

Focus topic: Endocrine disorders

After binding occurs, each hormone produces unique physiologic changes, depending on its target site and its specific action at that site. A particular hormone may have different effects at different target sites.

Hormonal regulation
A complex feedback mechanism involving hormones, the central nervous system (CNS), and blood chemicals and metabolites helps maintain the body’s delicate equilibrium by regulating hormone synthesis and secretion. Feedback refers to information sent to endocrine glands that signals the need for changes in hormone levels, either increasing or decreasing hormone production and release.

Endocrine disorders: Assessment

Focus topic: Endocrine disorders

To thoroughly assess the endocrine system, you must take an accurate health history and conduct a physical examination.

Endocrine disorders: History

Focus topic: Endocrine disorders

Because the endocrine system interacts with all other body systems, it’s important to ask the patient about his health history and current patterns of health and illness.

Current health status
Ask the patient to describe his chief complaint. Common complaints associated with endocrine disorders include fatigue, weakness, weight changes, mental status changes, polyuria, polydipsia, and abnormalities of sexual maturity and function.

Asking the tough questions

Focus topic: Endocrine disorders

Conduct a complete body systems review. Here are some examples of questions you might include:
• Have you noticed changes in your skin? If so, what kind?
• Do you feel tired?
• What are your sleep patterns?
• Have you noticed changes in your skin or changes in the amount or distribution of your body hair?
• Do your eyes burn or feel gritty when you close them?
• How good is your sense of smell?

Endocrine disorders

Previous health status
Ask about the patient’s medical history. You may identify insidious and vague symptoms of endocrine dysfunction by asking if the patient has had a skull fracture, surgery, complications of surgery, or brain infection, such as meningitis or encephalitis.

Family history
Ask about family history because certain endocrine disorders are inherited or have strong familial tendencies, such as diabetes mellitus, thyroid disease, and hypertension.

Lifestyle patterns
Ask the patient about temperature intolerance, which may indicate certain thryoid disorders. For example, intolerance to cold may indicate hypothyroidism, and intolerance to warmth, hyperthyroidism. Also ask what medications the patient is taking. Some medications can alter hormone secretion or receptor response.

Endocrine disorders: Physical examination

Focus topic: Endocrine disorders

Your physical examination should include a total body evaluation and a complete neurologic assessment because the hypothalamus plays an important role in regulating endocrine function through the pituitary gland. Begin by measuring the patient’s vital signs, height, and weight. Compare the findings with normal expected values and the patient’s baseline measurements, if available. Then inspect, palpate, and auscultate the patient to obtain the most objective findings.

Inspection
Systematically inspect the patient’s overall appearance and examine all areas of his body.

Appearances are revealing

Focus topic: Endocrine disorders

Assess the patient’s physical appearance and mental and emotional status. Note such factors as overall affect, speech, level of consciousness (LOC) and orientation, appropriateness and neatness of dress and grooming, and activity level. Evaluate general body development, including posture, body build, proportionality of body parts, and distribution of body fat.

Get the skinny on the skin

Focus topic: Endocrine disorders

Assess the patient’s overall skin color, temperature, thickness, and turgor, and inspect his skin and mucous membranes for lesions, bruising, or areas of increased, decreased, or absent pigmentation. As you do so, be sure to consider racial and ethnic variations. In a dark-skinned patient, color variations are best assessed in the sclera, conjunctiva, mouth, nail beds, and palms. Next, assess the patient’s skin texture and hydration.

A hairy situation

Focus topic: Endocrine disorders

Inspect the hair for amount, distribution, condition, and texture. Observe scalp and body hair for abnormal patterns of growth or hair loss. Again, remember to consider normal racial and ethnic — as well as gender — differences in hair growth and texture. Next, check the patient’s fingernails for cracking, peeling, separation from the nail bed (onycholysis), or clubbing; observe the toenails for fungal infection, ingrown nails, discoloration, length, and thickness.

Eyeing the head

Focus topic: Endocrine disorders

Assess the patient’s face for overall color and the presence of erythematous areas, especially in the cheeks. Note facial expression. Is it pained and anxious, dull and flat, or alert and interested? Note the shape and symmetry of the patient’s eyes, and look for eyeball protrusion, incomplete eyelid closure, or periorbital edema. Have the patient extend his tongue, and inspect it for color, size, lesions, positioning, and tremors or unusual movements.

Stick your neck out

Focus topic: Endocrine disorders

While standing in front of the patient, examine his neck — first with it held straight, then slightly extended, and finally while the patient swallows water. Check for neck symmetry and midline positioning and for symmetry of the trachea. Use tangential lighting directed downward from the patient’s chin to help you see the thyroid gland. An enlarged thyroid may be diffuse and asymmetrical.

Test the chest

Focus topic: Endocrine disorders

Evaluate the overall size, shape, and symmetry of the patient’s chest, noting deformities. In females, assess the breasts for size, shape, symmetry, pigmentation (especially on the nipples and in skin creases), and nipple discharge (galactorrhea). In males, observe for bilateral or unilateral breast enlargement (gynecomastia) and nipple discharge. Inspect the patient’s external genitalia — particularly the testes and clitoris — for normal development.

Extreme inspection

Inspect the patient’s extremities. Check the arms and hands for tremors. To do so, have the patient hold both arms outstretched in front with the palms down and fingers separated. Place a sheet of paper on the outstretched fingers and watch for trembling. Note any muscle wasting, especially in the upper arms, and have the patient grasp your hands to assess the strength and symmetry of his grip.
Next, inspect the legs for muscle development, symmetry, color, and hair distribution. Then assess muscle strength by having the patient sit on the edge of the examination table and extend his legs horizontally. A patient who can maintain this position for 2 minutes exhibits normal strength. Examine the feet for size, and note lesions, corns, calluses, or marks from socks or shoes. Inspect the toes and the spaces between them for maceration and fissures.

Endocrine disorders: Palpation

Focus topic: Endocrine disorders

Palpate the thyroid gland and testes, the only endocrine glands accessible to palpation. You won’t be able to palpate the thyroid gland in every patient. However, when you can examine the gland, it should be smooth, finely lobulated, nontender, and either soft or firm. You should be able to feel the gland’s sections.  A thyroid nodule feels like a knot, protuberance, or swelling; a firm, fixed nodule may be a tumor. Be careful not to confuse thick neck musculature with an enlarged thyroid or a goiter. The testes should be firm to palpation and about 3/4 (2 cm) long before puberty. By age 16, the testes should be about 13/4 (4.5 cm) long (normal range is 13/8 to 21/8 [3.5 to 5.5 cm]). Palpate the spermatic cord while the patient is standing.

Signs, signs, everywhere a sign

Focus topic: Endocrine disorders

Attempt to elicit Chvostek’s sign and Trousseau’s sign if you suspect a patient has hypocalcemia (low serum calcium levels) related to deficient or ineffective PTH secretion from hypoparathyroidism or surgical removal of the parathyroid glands. To elicit Chvostek’s sign, tap the facial nerve in front of the ear with a finger; if the facial muscles contract toward the ear, the test is positive for hypocalcemia. To elicit Trousseau’s sign, place a blood pressure cuff on the patient’s arm and inflate it above his systolic pressure. In a positive test, the patient will exhibit carpal spasm (ventral contraction of the thumb and digits) within 3 minutes.

Endocrine disorders: Auscultation

Focus topic: Endocrine disorders

If you palpate an enlarged thyroid, auscultate the gland for systolic bruits, a sign of hyperthyroidism. Bruits occur when accelerated blood flow through the thyroid arteries produces vibrations. To auscultate for bruits, place the bell of the stethoscope over one of the lateral lobes of the thyroid and then listen carefully for a low, soft, rushing sound. To ensure that tracheal sounds don’t obscure bruits, have the patient hold his breath while you auscultate.
To distinguish an arterial bruit from a venous hum, first listen for the rushing sound; then gently occlude the jugular vein with your fingers on the side you’re auscultating and listen again. A venous hum (produced by jugular blood flow) disappears during venous compression; an arterial bruit doesn’t.

Endocrine disorders

Endocrine disorders: Diagnostic tests

Focus topic: Endocrine disorders

Endocrine function is tested by direct, indirect, and provocative testing as well as radiographic studies.

Endocrine disorders: Direct testing

Focus topic: Endocrine disorders

The most common method, direct testing measures hormone levels in the blood or urine. However, accurate measurement requires special techniques because the body contains only minute hormone amounts.

Endocrine disorders

Endocrine disorders: Indirect testing

Focus topic: Endocrine disorders

Indirect testing measures the substance a particular hormone controls but not the hormone itself. For instance, glucose measurements help evaluate insulin, and calcium measurements help assess PTH activity. Although radioimmunoassays measure these substances directly, indirect testing is easier and less costly. Glucose levels obtained indirectly will accurately reflect insulin’s effectiveness, but various factors unrelated to an endocrine problem may affect calcium levels. For example, abnormal protein levels can lead to seemingly abnormal calcium levels because nearly one-half of calcium binds to plasma proteins. Therefore, rule out other possibilities before you assume that an abnormal calcium level reflects a PTH imbalance.

Endocrine disorders: Provocative testing

Focus topic: Endocrine disorders

Provocative testing helps determine an endocrine gland’s reserve function when other tests show borderline hormone levels or can’t quite pinpoint the abnormality’s site. For instance, an abnormally low cortisol level may indicate adrenal hypofunction or indirectly reflect pituitary hypofunction. Provocative testing works on this principle: Stimulate an underactive gland and suppress an overactive gland, depending on the patient’s suspected disorder. A hormone level that doesn’t increase with stimulation confirms primary hypofunction. Hormone secretion that continues after suppression confirms hyperfunction.

Endocrine disorders: Radiographic studies

Focus topic: Endocrine disorders

Radiographic studies are done with or after other tests. Computed tomography (CT) scans and magnetic resonance imaging (MRI) studies assess an endocrine gland by providing high-resolution, tomographic, three-dimensional images of the gland’s structure, whereas nuclear imaging studies help determine the cause of hyperthyroidism.
Routine X-rays help evaluate how an endocrine dysfunction affects body tissues, although they don’t reveal endocrine glands. For example, a bone X-ray, routinely ordered for a suspected parathyroid disorder, can show the effects of a calcium imbalance.

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