somatropin

somatropin /so·mat·ro·pin/ (so″mah-tro´pin) biosynthetic human growth hormone, prepared by recombinant means and having the same amino acid sequence as the natural hormone; used to treat growth failure and AIDS-associated cachexia or weight loss.

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hormone [hor´mōn]

a chemical transmitter substance produced by cells of the body and transported by the bloodstream to the cells and organs on which it has a specific regulatory effect. adj., adj hormo´nal. Hormones act as chemical messengers to body organs, stimulating certain life processes and retarding others. Growth, reproduction, control of metabolic processes, sexual attributes, and even mental conditions and personality traits are dependent on hormones.

Hormones are produced by various organs and body tissues, but mainly by the endocrine glands, such as the pituitary, thyroid, and gonads (testes and ovaries). Each gland apparently synthesizes several kinds of hormones; the adrenal glands alone produce more than 25 varieties. The total number of hormones is still unknown, but each has its unique function and its own chemical formula. After a hormone is discharged by its parent gland into the capillaries or the lymph, it may travel a circuitous path through the bloodstream to exert influence on cells, tissues, and organs (target organs) far removed from its site of origin.

One of the best-known endocrine hormones is insulin, a protein manufactured by the beta cells of the islands of Langerhans in the pancreas that is important in carbohydrate metabolism. Other important hormones are thyroxine, an iodine-carrying amino acid produced by the thyroid gland; cortisone, a member of the steroid family from the adrenal glands; and the sex hormones, estrogen from the ovaries and androgen from the testes. Certain hormone substances can be synthesized in the laboratory for treatment of human disease. Animal hormones can also be used, as endocrine hormones are to some extent interchangeable among species. Extracts from the pancreas of cattle, for example, enabled diabetes sufferers to live normal lives even before the chemistry of insulin was fully understood.

Endocrine hormone synthesis and secretion is controlled and regulated by a closed-loop system. Negative feedback loops maintain optimal levels of each hormone in the body. If there are abnormally high levels of a hormone in the blood, feedback to the gland responsible for its production inhibits secretion. If there are abnormally low levels, the gland is stimulated to step up production and secretion. In this way a homeostatic balance is maintained. (See also endocrine glands.)

adrenocortical hormone

1. any of the corticosteroids secreted by the adrenal cortex, the major ones being the glucocorticoids and mineralocorticoids, and including some androgens, progesterone, and estrogens.

2. corticosteroid.

adrenocorticotropic hormone (ACTH) corticotropin.

adrenomedullary h's substances secreted by the adrenal medulla, including epinephrine and norepinephrine.

androgenic hormone androgen.

anterior pituitary hormone any of the protein or polypeptide hormones secreted by the anterior lobe of the pituitary gland, including growth hormone, thyrotropin, prolactin, follicle-stimulating hormone, luteinizing hormone, melanocyte-stimulating hormone, and corticotropin.

antidiuretic hormone (ADH) vasopressin.

corpus luteum hormone progesterone.

cortical hormone corticosteroid.

corticotropin-releasing hormone (CRH) a neuropeptide secreted by the median eminence of the hypothalamus that binds to specific receptors on the corticotroph cells of the anterior pituitary and stimulates the secretion of corticotropin.

ectopic h's those secreted by tumors of nonendocrine tissues but having the same physiologic effects as their normally produced counterparts. It is not known exactly how the synthesis and secretion of endocrine hormones from nonendocrine tissues occurs. Most of these tumors are derived from tissues that have a common embryonic origin with endocrine tissues. When the cells undergo neoplastic transformation, they can revert to a more primitive stage of development and begin to synthesize hormones.

Ectopic hormones present serious problems for patients and add to the complexity of caring for those with certain kinds of neoplastic diseases. These hormones do not respond to the feedback mechanisms that regulate normal hormonal production; hence, surgery and destruction of the tumorous tissue by radiation and chemotherapy are the treatments of choice.

estrogenic hormone estrogen.

follicle-stimulating hormone (FSH) one of the gonadotropins of the anterior pituitary, which stimulates the growth and maturity of graafian follicles in the ovary, and stimulates spermatogenesis in the male.

follicle-stimulating hormone and luteinizing hormone–releasing hormone (FSH/LH-RH) luteinizing hormone–releasing hormone.

follicle-stimulating hormone–releasing hormone (FSH-RH) luteinizing hormone–releasing hormone.

gonadotropic hormone gonadotropin.

gonadotropin-releasing hormone (Gn-RH) luteinizing hormone–releasing hormone.

growth hormone (GH) any of several related polypeptide hormones secreted by the anterior lobe of the pituitary gland that directly influence protein, carbohydrate, and lipid metabolism and control the rate of skeletal and visceral growth; their secretion is in part controlled by the hypothalamus. It is used pharmaceutically as somatrem and somatropin. Called also somatotrophin, somatotropin, and somatotrophic or somatotropic hormone.

growth hormone release–inhibiting hormone somatostatin.

growth hormone–releasing hormone (GH-RH) a neuropeptide elaborated by the median eminence of the hypothalamus that binds to specific receptors on the somatotroph cells of the anterior pituitary and stimulates the secretion of growth hormone.

interstitial cell–stimulating hormone luteinizing hormone.

lactation hormone (lactogenic hormone) prolactin.

local hormone a substance with hormone like properties that acts at an anatomically restricted site; most are rapidly degraded. Called also autacoid and autocoid.

luteinizing hormone (LH) a gonadotropin of the anterior pituitary gland, acting with follicle-stimulating hormone to cause ovulation of mature follicles and secretion of estrogen by thecal and granulosa cells of the ovary; it is also concerned with corpus luteum formation. In the male, it stimulates development of the interstitial cells of the testes and their secretion of testosterone. Called also interstitial cell–stimulating hormone.

luteinizing hormone–releasing hormone (LH-RH) a decapeptide hormone of the hypothalamus, which stimulates the release of follicle-stimulating hormone and luteinizing hormone from the pituitary gland; it can be used in the differential diagnosis of hypothalamic, pituitary, and gonadal dysfunction. Called also follicle-stimulating hormone–releasing hormone, follicle-stimulating hormone and luteinizing hormone–releasing hormone, and gonadotropin-releasing hormone.

melanocyte-stimulating hormone (MSH) a substance from the anterior pituitary gland of certain other animals but not humans; it influences the formation or deposition of melanin in the body and pigmentation of the skin.

neurohypophyseal h's those stored and released by the neurohypophysis, i.e., oxytocin and vasopressin.

parathyroid hormone (PTH) a polypeptide hormone secreted by the parathyroid glands that influences calcium and phosphorus metabolism and bone formation.

placental h's hormones secreted by the placenta, including chorionic gonadotropin, and other substances having estrogenic, progestational, or adrenocorticoid activity.

progestational hormone

1. progesterone.

2. progestational agent.

prolactin-inhibiting hormone a hormone released by the hypothalamus that inhibits the secretion of prolactin by the anterior pituitary gland.

prolactin-releasing hormone any of various hormones elaborated by the hypothalamus that stimulate the release of prolactin by the anterior pituitary gland. Most such activity is exerted by vasoactive intestinal polypeptide, although in humans thyrotropin-releasing hormone can also have this action.

sex h's see sex hormones.

somatotrophic hormone (somatotropic hormone) growth hormone.

somatotropin release–inhibiting hormone somatostatin.

somatotropin-releasing hormone (SRH) growth hormone–releasing hormone.

steroid h's hormones that are biologically active steroids; they are secreted by the adrenal cortex, testis, ovary, and placenta and include the progestational agents, glucocorticoids, mineralocorticoids, androgens, and estrogens. They act by binding to specific receptors to form complexes, which then enhance or inhibit the expression of specific genes.

thyroid h's see thyroid hormones.

thyroid-stimulating hormone (TSH) thyrotropin.

thyrotropin-releasing hormone (TRH) a tripeptide hormone of the hypothalamus, which stimulates release of thyrotropin from the pituitary gland. In humans, it also acts as a prolactinreleasing factor. It is used in the diagnosis of mild hyperthyroidism and Graves disease, and in differentiating between primary, secondary, and tertiary hypothyroidism.

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somatropin

nonproprietary drug name for somatotropin (growth hormone).

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somatropin, recombinant

Genotropin, Humatrope, Norditropin, Nutropin AQ, Nutropin AQ Pen, Nutropin Depot, Saizen, Serostim, Tev-Tropin, Zomacton (UK), Zorbtive

Pharmacologic class: Posterior pituitary hormone

Therapeutic class: Growth hormone (GH)

Pregnancy risk category B (Genotropin, Saizen, Serostim), C

Action

Stimulates linear and skeletal growth, increases number and size of muscle cells, and influences internal organ size

Availability

Genotropin injection: 1.5 mg (about 4 international units/vial), 5.8 mg (about 15 international units/vial), 13.8 mg (about 41.4 international units/vial)

Humatrope injection: 2 mg (about 6 international units/vial), 5 mg (about 15 international units/vial), 6 mg (about 18 international units/vial), 12 mg (about 36 international units/vial), 24 mg (about 72 international units/vial)

Norditropin injection: 4 mg (12 international units/vial), 8 mg (24 international units/vial)

Norditropin injection cartridge: 5 mg/1.5 ml, 10 mg/1.5 ml, 15 mg/1.5 ml

Nutropin AQ injection: 10 mg

Nutropin AQ Pen injection cartridge: 10 mg

Nutropin Depot: 13.5-mg, 18-mg, and 22.5-mg single-use vials; 13.5-mg, 18-mg, and 22.5-mg kits

Nutropin injection: 5 mg (about 15 international units/vial), 10 mg (about 30 international units/vial)

Saizem injection: 5 g (about 15 international units/vial)

Serostim injection: 5 mg (about 15 international units/vial), 6 mg (about 18 international units/vial)

Tev-Tropin injection: 5 mg

Zorbtive injection: 8.8 mg in 10-ml vial

⊘Indications and dosages

➣ Growth failure in children with inadequate endogenous GH

Children: 0.16 to 0.24 mg/kg (Genotropin) subcutaneously q week in six or seven divided doses. Or 0.18 mg/kg/week (Humatrope) subcutaneously or I.M., divided equally and given on three alternate days six times weekly (or daily, if epiphyseal closure hasn't occurred). Or 0.024 to 0.034 mg/kg (Norditropin) subcutaneously six or seven times each week using NordiPen injection pen. Or 0.3 mg/kg/week (Nutropin AQ, Nutropin AQ Pen, Tev-Tropin) subcutaneously in equally divided daily doses. Or 0.06 mg/kg (Saizen) subcutaneously or I.M. three times weekly.

➣ Endogenous GH replacement in adults with GH deficiency

Adults: 0.04 mg/kg/week (Genotropin) subcutaneously in six or seven divided doses. Or 0.006 mg/kg/day (Humatrope) subcutaneously. Or initially, no more than 0.006 mg/kg/day (Nutropin AQ, Nutropin AQ Pen, Tev-Tropin) subcutaneously; may increase to a maximum of 0.025 mg/kg daily in patients younger than age 35 or 0.0125 mg/kg/day in patients ages 35 and older. Or 0.005 mg/kg/day (Saizen) subcutaneously; may increase to a maximum of 0.01 mg/kg/day after 4 weeks, depending on patient tolerance.

➣ Short stature related to Turner's syndrome

Children: 0.375 mg/kg/week (Humatrope) subcutaneously, divided into equal doses given on 3 alternate days or daily. Or up to 0.375 mg/kg/week (Nutropin AQ, Nutropin AQ Pen) subcutaneously, divided into equal doses given three or seven times weekly.

➣ Idiopathic short stature (non-GH-deficient) in children whose epiphyses haven't closed

Children: Up to 0.37 mg/kg (Humatrope) subcutaneously q week. Divide dosage and give in equal doses six or seven times weekly.

➣ Growth failure in children with Prader-Willi syndrome

Children: 0.24 mg/kg/week (Genotropin) subcutaneously in six or seven divided doses

➣ Infants born small for gestational age

Children: 0.48 mg/kg/week (Genotropin) subcutaneously in six or seven divided doses

➣ AIDS wasting or cachexia

Adults and children weighing more than 55 kg (121 lb): 6 mg (Serostim) subcutaneously at bedtime

Adults and children weighing 45 to 55 kg (99 to 121 lb): 5 mg (Serostim) subcutaneously at bedtime

Adults and children weighing 35 to 45 kg (77 to 99 lb): 4 mg (Serostim) subcutaneously at bedtime

Adults and children weighing less than 35 kg (77 lb): 0.1 mg/kg/day (Serostim) subcutaneously at bedtime

➣ Growth failure due to chronic renal insufficiency (up to time of kidney transplantation)

Children: Up to 0.35 mg/kg/weekly (Nutropin AQ, Nutropin AQ Pen) subcutaneously, divided into daily doses

➣ Short bowel syndrome in patients receiving specialized nutritional support

Adults: 0.1 mg/kg/day subcutaneously (Zorbtive), to a maximum of 8 mg/day for no more than 4 weeks

Contraindications

• Hypersensitivity to drug, benzyl alcohol, glycerin, or metacresol (with some diluents)
• Active neoplasia
• Acute, critical illness after open-heart surgery, acute respiratory failure, or multiple trauma
• Children with closed epiphyses
• Neonates (Zorbtive)

Precautions

Use cautiously in:
• hypothyroidism
• diabetes mellitus.

Administration

• Reconstitute by injecting supplied diluent through rubber top of vial and aiming liquid stream at side of vial. Swirl vial gently to mix; don't shake.
• Inspect reconstituted solution. Don't use if it has visible particles or is cloudy.
• Keep diluted drug refrigerated; use within 14 days.
• When using prefilled cartridges, follow manufacturer's instructions carefully.
• Know that patients receiving Zorbtive for short bowel syndrome may receive specialized nutritional support as needed.

Route	Onset	Peak	Duration
I.M., subcut.	Unknown	1-5 hr	12-48 hr

Adverse reactions

CNS: headache, weakness

CV: mild and transient edema

GU: hypercalciuria

Hematologic: leukemia

Metabolic: fluid retention, mild hyperglycemia, hypothyroidism, ketosis

Musculoskeletal: localized muscle pain, tissue swelling, joint pain

Skin: rash, urticaria

Other: pain, inflammation at injection site

Interactions

Drug-drug. Androgens, thyroid hormone: epiphyseal closure

Corticotrophin, corticosteroids: inhibited growth response (with long-term use)

Drug-diagnostic tests. Alkaline phosphatase, glucose, inorganic phosphorus, parathyroid hormone: increased levels

Patient monitoring

• Monitor patient's height, X-rays, blood chemistry results, blood glucose level, and thyroid function studies.
☞ Watch for signs and symptoms of leukemia.

Patient teaching

• Advise patient and parents that regular check-ups and blood tests are needed to detect adverse reactions.
• Teach parents how to reconstitute and administer drug. Stress importance of following manufacturer's instructions carefully when using prefilled cartridges.
• Teach parents about proper handling and disposal of syringes, needles, and cartridges.
• As appropriate, review all significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above.