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SANDRA REYNOLDS, a 64-year-old homeless woman, is admitted toyour unit for rehabilitation afterbeing injured by a hit-and-rundriver. She sustained a compoundpelvic fracture and several contu-sions and abrasions. Ms. Reynoldshas not had regular medical carefor several years. She’s 5'3", weighs185 pounds, and has thinninggray-brown hair. Her skin is dryand rough, and she says she fre-quently feels cold. Ms. Reynoldslooks much older than her statedage and has little interest in any-thing except sleeping. When shetalks to you, her voice is hoarseand her speech is slow. She is con-stipated. Ms. Reynolds’ vital signsare: heart rate 56 beats/minute,blood pressure 143/82 mm Hg, tem-perature 97.4° F (36.3° C), andrespiratory rate 14 breaths perminute. As an inpatient rehab nurse

working with Ms. Reynolds, you ob-serve her lack of energy, mentalstate, and aged appearance. All ofthese findings are attributable, youreason, to her recent trauma andthe effects of homelessness. But afterreading this article, you should alsothink about hypothyroidism as a po-tential source of her signs andsymptoms.

Hypothyroidism, also known asmyxedema, is second to diabetesmellitus as the most common en-docrine disorder in the UnitedStates. It’s six times more likely tooccur in women than men and ismore common in older people.About 10% of women over age 60have subclinical hypothyroidism.Because it affects all of the body’s

systems, mimicking many other dis-ease processes, hypothyroidism canbe overlooked as an explanationfor a patient’s clinical presentation.This article reviews the pathophysi-ology of hypothyroidism, as well asits causes, symptoms, diagnosis,treatment, and nursing care.

About the thyroidThe thyroid’s main job is as masterregulator of metabolism. It’s locatedin the front of the neck, below thelarynx and in front of the trachea. Ithas two lobes, giving it a butterflyshape. The thyroid produces twohormones, thyroxine (T4) and tri-

Hypothyroidism and nursing careLearn to recognize the symptoms of this commonly

overlooked condition.By Dorothy Moore, DNP, FNP-C, CCRN

Understanding the HPT axisThyroid homeostasis is maintained through the hypothalamic-pituitary-thyroid(HPT) axis.The hypothalamus secretes thyrotropin-releasing hormone (TRH), which signals

the anterior pituitary to secrete thyroid-stimulating hormone (TSH). TSH then signalsthe thyroid to produce thyroxine (T4) and triiodothyronine (T3). When levels of thy-roid hormone are sufficient, release of TRH and TSH are reduced through negativefeedback inhibition. To stimulate the production of thyroid hormones, the body needs approximately

1 mg of iodine a week. T4 makes up 90% of the hormone secreted by the thyroid;the remaining portion is T3. However, T3 is about four times more potent than T4.Most T3 and T4 is bound to serum proteins; only about 1% is unbound and free to

enter cells to carry out thyroid functions.

TRH = Thyrotropin-releasing hormone

TSH = Thyroid-stimulating hormone

T3 = Triiodothyronine hormone

T4 = Thyroxine hormoneTRH

TSH

Hypothalamus

Thyroidgland

Pituitary gland

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iodothyronine (T3), by extractingiodine from the blood. Thyroidcells are the only cells in the bodythat absorb and use iodine. Everycell in the human body relies on T3and T4 to manage its metabolism.

To regulate T3 and T4 produc-tion, the thyroid works in a feed-back loop with the hypothalamusand the anterior pituitary gland,which is called the hypothalamic-pituitary-thyroid (HPT) axis. (SeeUnderstanding the HPT axis.)

Primary hypothyroidism occurswhen the thyroid is damaged andcan’t produce T3 and T4. Second-ary hypothyroidism is caused by pi-tuitary gland dysfunction, and terti-ary hypothyroidism results fromproblems with the hypothalamus.This article focuses on the mostcommon thyroid problem—primaryhypothyroidism.

Causes of primaryhypothyroidismThe most common cause of hypo -thyroidism is autoimmune thyroidi-tis, or Hashimoto’s thyroiditis; dam-age to the thyroid through surgery,ablation, or radiation treatment areless common causes. Other autoim-mune diseases, such as sclerodermaor amyloidosis, can cause hypo -thyroidism

A rare outcome of hypothyroid -ism is myxedema coma, which issevere physiologic decompensa-tion that can lead to death. Myx -edema coma is a true medicalemergency with a high mortalityrate, but with iodized salt and im-proved medical surveillance, theannual incidence is only 0.22 permillion population.

Symptoms of hypothyroidismMs. Reynolds’ skin is pale and cool,which is common in patients withhypothyroidism. Because the turn -over of new cells is delayed withslowed metabolism, her skin has acharacteristic dry, rough quality.Ms. Reynolds’ face is puffy, and hervoice is hoarse because of tongue

enlargement. She has coarse, thin-ning hair, brittle fingernails, andperiorbital edema. These are allfindings associated with hypothy-roidism.

People with hypothyroidism ex-perience a slowing of metabolicprocesses, which can result in fa-tigue, slow speech, constipation,cold intolerance, weight gain,bradycardia, and decreased deeptendon reflexes. One study showed

the most common symptoms aretiredness, dry skin, and shortness ofbreath. The signs of hypothyroidismare numerous, often subtle, and notspecific to hypothyroidism. (See Rec -ognizing hypothyroid symptoms.)

Diagnosis Hypothyroidism can masquerade asvitamin B12 or D deficiency, irondeficiency, chronic kidney disease,obstructive sleep apnea, or viral in-

Hypothyroidism affects every body system. Some key symptoms are listed below.

Body system Hypothyroid symptoms

Cardiac • Bradycardia (can reduce cardiac output and decrease endurance) • Heart enlargement (late-stage hypothyroidism) • Flattened T waves • Hypertension

Central nervous • Cold intolerancesystem/metabolic • Elevated cholesterol levels • Excessive sleep and fatigue • Slowed thinking and inability to concentrate • Weight gain

Ear, nose, and throat • Enlarged tongue • Goiter • Puffy eyes

Integumentary • Brittle nails • Coarse, thinning hair • Dry skin that looks older than stated age • Loss of body hair

Genitourinary Women: • Heavy periods • Infertility • Irregular periods Men: • Decreased libido • Delayed ejaculation • Erectile dysfunction

Gastrointestinal • Celiac disease (four times more common in patients with hypothyroidism than in the general population) • Constipation • Decreased taste sensation • Gastric atrophy resulting in pernicious anemia

Musculoskeletal • Carpal tunnel syndrome • Muscle weakness and cramping • Slowed reflexes

Recognizing hypothyroid symptoms

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fections, such as mononucleosis.Because symptoms overlap with somany other conditions, diagnosinghypothyroidism based on clinicalpresentation alone is not possible;laboratory testing is required.

Fortunately, we can measure thy-roid hormone levels in the bloodand pinpoint a diagnosis. As a nurse,you can expect orders for lab drawsof serum thyroid-stimulating hor-mone (TSH) and possibly free T4.(Free T4 is not bound to protein, soit can be used by the body.) You’llwant to be able to understand andexplain the purpose of these labtests to your patients.• Hypothyroidism is diagnosed

when a person has an elevatedserum TSH level and a lowserum free T4 level.

• If a patient’s TSH level is elevat-ed, but the serum free T4 is low,then the likely diagnosis is sub-clinical hypothyroidism.

• A low serum-free T4 level with anormal TSH may indicate a sec-ondary cause of hypothyroidism,and further testing will be doneto look at hypothalamic-pituitarygland insufficiency. (See Diag-nosing hypothyroidism.)

TreatmentHypothyroidism is treated with syn-thetic T4 (levothyroxine), which isavailable in tablet, soft gel, and liq-uid form, although tablet is themost common. Studies show nobenefit to taking both T4 and T3,

since T4 is converted to T3 in theperipheral tissues. Generic and pro-prietary formulations of T4 areequally effective, but switchingback and forth isn’t recommended.Patients remain on thyroid monitor-ing and supplementation for life.

Nursing considerationsTeach patients about the many druginteractions with levothyroxine andabout the importance of establish-ing a daily routine to help maintaineven hormone levels. Levothyrox-ine should be taken on an emptystomach with water, at least 1 hourbefore eating. Even coffee has beenshown to interfere with the absorp-tion of T4. And levothyroxine isincompatible with many othermedications, so it should be takenalone. Medications that bind withlevothyroxine and reduce its bio -availability include bile acid seques-trants (such as sevelamer), calciumsupplements (including calcium ac-etate, carbonate, and citrate), alu-minum, magnesium, lanthanum,and simethicone.

Taking levothyroxine with antico-agulants can increase the effect ofanticoagulants. With some medica-tions, such as antacids, advise pa-tients to allow 4 to 6 hours to passbetween taking each medication.

Although patients are traditional-ly instructed to take levothyroxinefirst thing in the morning on anempty stomach, a randomized dou-ble-blind study showed that taking

it at bedtime results in better ab-sorption. This schedule change maybe particularly helpful for patientswho take many medications in themorning that are incompatible withlevothyroxine.

PrognosisAfter beginning levothyroxine, symp -tom improvement can take up to 6weeks, and dosing may need to betitrated, which is usually done at 3-to 6-week intervals. Patients shouldbegin to feel a restored sense ofenergy, improved cognitive func-tion, thickening of hair, and othersymptom improvements. You suggest to Ms. Reynolds’ pro -

vider that perhaps she has hypo -thyroidism. TSH and T4 levels areordered, and your suspicions areconfirmed—her TSH is 7.5 mlU/Land her T4 level is 3.9 mcg/dL.Levothyroxine is ordered. Over thecourse of the next 2 weeks of her re-hab, Ms. Reynolds begins to feelmore energetic and involved in hercare, she’s more alert, and she’swilling to talk with a caseworkerabout transitional housing. Yourastute call enabled her to get thetreatment she needed to improveher quality of life.

Visit americannursetoday.com/?p=37703 fora list of selected references.

Dorothy Moore is a staff nurse at Kaiser PermanenteEmergency Department, in Oakland, California, andan adjunct lecturer at California State University inHayward.

Hypothyroidism can be mistaken for several other conditions. Measuring thyroid hormone levels in the blood is the only way tomake a definitive diagnosis.

Hormone Typical normal range Hypothyroidism Hyperthyroidism Secondary hypothyroidism

TSH 0.5 to 5.0 mIU/L > 5.0 mIU/L < 0.4 mIU/L < 0.4 mIU/L (Varies by age. < 2.5 mIU/L is typical goal when patient is taking levothyroxine.)

T4 4.6-12 mcg/dL < 4.6 mcg/dL > 12 mcg/dL < 4.6 mcg/dL

T4 = thyroxine; TSH = thyroid-stimulating hormone

Diagnosing hypothyroidism