SECTION 11 Problems Related to Regulatory and Reproductive Mechanisms
52
Assessment: Endocrine System
Julia A. Hitch
http://evolve.elsevier.com/Lewis/medsurg/
CONCEPTUAL FOCUS
Homeostasis Reproduction
Hormonal Regulation Stress
LEARNING OUTCOMES
1. Describe the common characteristics and functions of 6. Link age-related changes in the endocrine system to
hormones. differences in assessment findings.
2. Identify the locations of the endocrine glands. 7. Distinguish normal from common abnormal findings of a
3. Describe the functions of hormones secreted by the pituitary, physical assessment of the endocrine system.
thyroid, parathyroid, and adrenal glands and the pancreas. 8. Describe the purpose, significance of results, and nursing
4. Obtain significant subjective and objective assessment data responsibilities related to diagnostic studies of the
related to the endocrine system from a patient. endocrine system.
5. Perform a physical assessment of the endocrine system
using the appropriate techniques.
KEY TERMS
aldosterone insulin
antidiuretic hormone (ADH) negative feedback
catecholamines positive feedback
circadian rhythm thyroxine (T4)
corticosteroid triiodothyronine (T3)
cortisol tropic hormones
hormones
STRUCTURES AND FUNCTIONS OF reproduction, (4) maintaining homeostasis, and (5) responding
ENDOCRINE SYSTEM to emergency demands.
Glands Hormones
Endocrine glands include the hypothalamus, pituitary, thyroid, Hormones are chemical substances made by endocrine glands that
parathyroids, adrenals, pancreas, ovaries, testes, and pineal control and regulate the activity of certain target cells or organs.
gland (Fig. 52.1). These glands make and release special chem- Many are made in one part of the body and control and regulate the
ical messengers called hormones. The endocrine system has 5 activity of certain cells or organs in another part of the body. The
general functions: (1) a role in reproductive and central nervous thyroid gland makes the hormone thyroxine, which affects many
system (CNS) development in the fetus, (2) stimulating growth body tissues when released directly into the circulation. Other hor-
and development during childhood and adolescence, (3) sexual mones act locally on cells where they are released and never enter
1265
,1266 SECTION 11 Problems Related to Regulatory and Reproductive Mechanisms
Hypothalamus mechanism. This means a hormone will act only on cells with a
receptor specific to that hormone (Fig. 52.2).
Pituitary
Pineal
Lipid-Soluble and Water-Soluble Hormones
We classify hormones by their chemical structure as lipid sol-
Parathyroids Thyroid uble or water soluble. The difference in solubility is important
in understanding how the hormone interacts with the target
Thymus
cell (Fig. 52.3). Lipid-soluble hormones (steroids, thyroid) are
bound to plasma proteins as they travel to target cells. They
cross the cell membrane by simple diffusion. Water-soluble
Adrenals hormones (insulin, growth hormone [GH], prolactin) circulate
freely in the blood and act directly on target tissues.
Pancreas
(islets)
Regulation of Hormonal Secretion
Specific mechanisms control endocrine activity by either stim-
ulating or inhibiting hormone synthesis and secretion. These
include positive and negative feedback, nervous system control,
and physiologic rhythms.
Simple feedback. Negative feedback relies on the blood
level of a hormone or other chemical compound regulated by
the hormone (e.g., glucose). It is the most common type of
endocrine feedback system. It results in the gland increasing or
Ovaries
decreasing the release of a hormone. An example of negative
(female) feedback is calcium and parathyroid hormone (PTH) regulation.
Testes Low blood levels of calcium stimulate the parathyroid gland to
(male) release PTH. PTH acts on the bone, intestine, and kidneys to
Fig. 52.1 Location of the major endocrine glands. The parathyroid increase blood calcium levels. The increased blood calcium level
glands lie on the posterior surface of the thyroid gland. (Modified from then inhibits further PTH release (Fig. 52.4).
Patton KT, Thibodeau GA: Anatomy and physiology, ed 8, St Louis, With positive feedback, increasing hormone levels cause
2013, Mosby.) another gland to release a hormone that stimulates further
release of the first hormone. Something must stop the release
the bloodstream. We call this local effect paracrine action. The of the first hormone (e.g., follicle death), or its release will con-
action of sex steroids on the ovary is an example of paracrine action. tinue. The ovarian hormone estradiol works by this type of
Most hormones have common characteristics. They are (1) feedback. Increased estradiol levels made by the follicle during
secreted in small amounts at variable but predictable rates, (2) the menstrual cycle result in the production and release of fol-
regulated by feedback systems, and (3) able to bind to specific licle-stimulating hormone (FSH) by the anterior pituitary. FSH
target cell receptors. Table 52.1 reviews the main hormones, the causes further increases in estradiol until the death of the folli-
glands or tissues that make the hormones, their target organs or cle. This results in a drop in FSH serum levels.
tissues, and their functions. Nervous system control. Nervous system activity directly
The endocrine system and nervous system have a strong con- affects some endocrine glands. Pain, fear, sexual excitement,
nection. Catecholamines (e.g., epinephrine), secreted by the adre- and other stressors can stimulate the nervous system to control
nal gland, travel through the bloodstream and affect multiple organ hormone secretion. For example, when the CNS senses or
systems. When secreted by nerve cells in the brain and peripheral perceives stress, the sympathetic nervous system (SNS) secretes
nervous system, these same substances act as neurotransmitters, catecholamines (e.g., epinephrine), which maximize heart and
sending important impulses across nerve synapses. lung function and vision to deal with the stress more effectively.
Organs can act as endocrine glands by secreting hormones. Chronic exposure to some stressors can cause persistent
For example, the kidneys secrete erythropoietin. It stimulates increases in heart rate and BP and changes in the endocrine
red blood cell production. The heart secretes atrial natri- system. This puts patients at risk for chronic disease, such
uretic peptide (ANP). The gastrointestinal (GI) tract secretes as hypertension and heart disease. Stress-related effects are
many peptide hormones (e.g., gastrin) that aid in digestion. discussed in Chapter 7.
These hormones are discussed in their respective assessment Rhythms. A common physiologic rhythm is the circadian
chapters. rhythm. It is a 24-hour rhythm that is driven by sleep-wake or
dark-light 24-hour (diurnal) cycles. Hormone levels and the
Hormone Receptors responsiveness of target tissues fluctuate predictably during
Hormones exert their effects by recognizing their target tis- these cycles. Cortisol, made by the adrenal cortex, rises early
sues and attaching to receptor sites in a “lock-and-key” type of in the day, declines toward evening, and rises again toward
, CHAPTER 52 Assessment: Endocrine System 1267
TABLE 52.1 Endocrine Glands and Hormones
Hormones Target Tissue Functions
Anterior Pituitary (Adenohypophysis)
Adrenocorticotropic hormone (ACTH) Adrenal cortex Fosters growth of adrenal cortex
Stimulates corticosteroid secretion
Gonadotropic hormones Reproductive organs Stimulates sex hormone secretion, reproductive organ growth, reproductive
• Follicle-stimulating hormone (FSH) processes
• Luteinizing hormone (LH)
Growth hormone (GH), or somatotropin All body cells Promotes protein anabolism (growth, tissue repair) and lipid mobilization and
catabolism
Melanocyte-stimulating hormone (MSH) Melanocytes in skin ↑ Melanin production in melanocytes
Prolactin Ovary and mammary Stimulates milk production in lactating women. ↑ Response of follicles to LH
glands in women and FSH
Testes in men Stimulates testicular function in men
Thyroid-stimulating hormone (TSH), or thyrotropin Thyroid gland Stimulates synthesis and release of thyroid hormones, growth and function of
thyroid gland
Posterior Pituitary (Neurohypophysis)
Antidiuretic hormone (ADH) Renal tubules, vascular Promotes reabsorption of water from the renal tubules, vasoconstriction
smooth muscle
Oxytocin Uterus, mammary glands Stimulates milk secretion, uterine contractility
Thyroid
Calcitonin Bone tissue Regulates calcium and phosphorus serum levels. ↓ Serum Ca2+ levels
Thyroxine (T4) All body tissues Precursor to T3
Triiodothyronine (T3) All body tissues Regulates metabolic rate of all cells and processes of cell growth and tissue
differentiation
Parathyroids
Parathyroid hormone (PTH) or parathormone Bone, intestine, kidneys Regulates calcium and phosphorus serum levels. Promotes bone
demineralization and ↑ intestinal absorption of Ca2+. ↑ Serum Ca2+ levels
Adrenal Medulla
Epinephrine (adrenaline) Catecholamine ↑ In response to stress. Enhances and prolongs effects of sympathetic nervous
system
Norepinephrine (noradrenaline) Catecholamine ↑ In response to stress. Enhances and prolongs effects of sympathetic nervous
system
Adrenal Cortex
Androgens (e.g., dehydroepiandrosterone Reproductive organs Promotes growth spurt in adolescence, secondary sex characteristics, and libido
[DHEA], androsterone) and estradiol in both sexes
Corticosteroids (e.g., cortisol, hydrocortisone) All body tissues Promotes metabolism. ↑ In response to stress. Antiinflammatory
Mineralocorticoids (e.g., aldosterone) Kidney Regulates sodium and potassium balance and thus water balance
Pancreas (Islets of Langerhans)
Amylin (from β cells) Liver, stomach ↓ Gastric motility, glucagon secretion, and endogenous glucose release from
liver. ↑ Satiety
Glucagon (from α cells) General Stimulates glycogenolysis and gluconeogenesis
Insulin (from β cells) General Promotes glucose transport from the blood into the cell
Pancreatic polypeptide General Influences regulation of pancreatic exocrine function and metabolism of
absorbed nutrients
Somatostatin Pancreas Inhibits insulin and glucagon secretion
Gonads
Women: Ovaries
Estrogen Reproductive system, breasts Stimulates development of secondary sex characteristics, preparation of uterus
for fertilization, and fetal development. Stimulates bone growth
Progesterone Reproductive system Maintains lining of uterus needed for successful pregnancy
Men: Testes
Testosterone Reproductive system Stimulates development of secondary sex characteristics, spermatogenesis
52
Assessment: Endocrine System
Julia A. Hitch
http://evolve.elsevier.com/Lewis/medsurg/
CONCEPTUAL FOCUS
Homeostasis Reproduction
Hormonal Regulation Stress
LEARNING OUTCOMES
1. Describe the common characteristics and functions of 6. Link age-related changes in the endocrine system to
hormones. differences in assessment findings.
2. Identify the locations of the endocrine glands. 7. Distinguish normal from common abnormal findings of a
3. Describe the functions of hormones secreted by the pituitary, physical assessment of the endocrine system.
thyroid, parathyroid, and adrenal glands and the pancreas. 8. Describe the purpose, significance of results, and nursing
4. Obtain significant subjective and objective assessment data responsibilities related to diagnostic studies of the
related to the endocrine system from a patient. endocrine system.
5. Perform a physical assessment of the endocrine system
using the appropriate techniques.
KEY TERMS
aldosterone insulin
antidiuretic hormone (ADH) negative feedback
catecholamines positive feedback
circadian rhythm thyroxine (T4)
corticosteroid triiodothyronine (T3)
cortisol tropic hormones
hormones
STRUCTURES AND FUNCTIONS OF reproduction, (4) maintaining homeostasis, and (5) responding
ENDOCRINE SYSTEM to emergency demands.
Glands Hormones
Endocrine glands include the hypothalamus, pituitary, thyroid, Hormones are chemical substances made by endocrine glands that
parathyroids, adrenals, pancreas, ovaries, testes, and pineal control and regulate the activity of certain target cells or organs.
gland (Fig. 52.1). These glands make and release special chem- Many are made in one part of the body and control and regulate the
ical messengers called hormones. The endocrine system has 5 activity of certain cells or organs in another part of the body. The
general functions: (1) a role in reproductive and central nervous thyroid gland makes the hormone thyroxine, which affects many
system (CNS) development in the fetus, (2) stimulating growth body tissues when released directly into the circulation. Other hor-
and development during childhood and adolescence, (3) sexual mones act locally on cells where they are released and never enter
1265
,1266 SECTION 11 Problems Related to Regulatory and Reproductive Mechanisms
Hypothalamus mechanism. This means a hormone will act only on cells with a
receptor specific to that hormone (Fig. 52.2).
Pituitary
Pineal
Lipid-Soluble and Water-Soluble Hormones
We classify hormones by their chemical structure as lipid sol-
Parathyroids Thyroid uble or water soluble. The difference in solubility is important
in understanding how the hormone interacts with the target
Thymus
cell (Fig. 52.3). Lipid-soluble hormones (steroids, thyroid) are
bound to plasma proteins as they travel to target cells. They
cross the cell membrane by simple diffusion. Water-soluble
Adrenals hormones (insulin, growth hormone [GH], prolactin) circulate
freely in the blood and act directly on target tissues.
Pancreas
(islets)
Regulation of Hormonal Secretion
Specific mechanisms control endocrine activity by either stim-
ulating or inhibiting hormone synthesis and secretion. These
include positive and negative feedback, nervous system control,
and physiologic rhythms.
Simple feedback. Negative feedback relies on the blood
level of a hormone or other chemical compound regulated by
the hormone (e.g., glucose). It is the most common type of
endocrine feedback system. It results in the gland increasing or
Ovaries
decreasing the release of a hormone. An example of negative
(female) feedback is calcium and parathyroid hormone (PTH) regulation.
Testes Low blood levels of calcium stimulate the parathyroid gland to
(male) release PTH. PTH acts on the bone, intestine, and kidneys to
Fig. 52.1 Location of the major endocrine glands. The parathyroid increase blood calcium levels. The increased blood calcium level
glands lie on the posterior surface of the thyroid gland. (Modified from then inhibits further PTH release (Fig. 52.4).
Patton KT, Thibodeau GA: Anatomy and physiology, ed 8, St Louis, With positive feedback, increasing hormone levels cause
2013, Mosby.) another gland to release a hormone that stimulates further
release of the first hormone. Something must stop the release
the bloodstream. We call this local effect paracrine action. The of the first hormone (e.g., follicle death), or its release will con-
action of sex steroids on the ovary is an example of paracrine action. tinue. The ovarian hormone estradiol works by this type of
Most hormones have common characteristics. They are (1) feedback. Increased estradiol levels made by the follicle during
secreted in small amounts at variable but predictable rates, (2) the menstrual cycle result in the production and release of fol-
regulated by feedback systems, and (3) able to bind to specific licle-stimulating hormone (FSH) by the anterior pituitary. FSH
target cell receptors. Table 52.1 reviews the main hormones, the causes further increases in estradiol until the death of the folli-
glands or tissues that make the hormones, their target organs or cle. This results in a drop in FSH serum levels.
tissues, and their functions. Nervous system control. Nervous system activity directly
The endocrine system and nervous system have a strong con- affects some endocrine glands. Pain, fear, sexual excitement,
nection. Catecholamines (e.g., epinephrine), secreted by the adre- and other stressors can stimulate the nervous system to control
nal gland, travel through the bloodstream and affect multiple organ hormone secretion. For example, when the CNS senses or
systems. When secreted by nerve cells in the brain and peripheral perceives stress, the sympathetic nervous system (SNS) secretes
nervous system, these same substances act as neurotransmitters, catecholamines (e.g., epinephrine), which maximize heart and
sending important impulses across nerve synapses. lung function and vision to deal with the stress more effectively.
Organs can act as endocrine glands by secreting hormones. Chronic exposure to some stressors can cause persistent
For example, the kidneys secrete erythropoietin. It stimulates increases in heart rate and BP and changes in the endocrine
red blood cell production. The heart secretes atrial natri- system. This puts patients at risk for chronic disease, such
uretic peptide (ANP). The gastrointestinal (GI) tract secretes as hypertension and heart disease. Stress-related effects are
many peptide hormones (e.g., gastrin) that aid in digestion. discussed in Chapter 7.
These hormones are discussed in their respective assessment Rhythms. A common physiologic rhythm is the circadian
chapters. rhythm. It is a 24-hour rhythm that is driven by sleep-wake or
dark-light 24-hour (diurnal) cycles. Hormone levels and the
Hormone Receptors responsiveness of target tissues fluctuate predictably during
Hormones exert their effects by recognizing their target tis- these cycles. Cortisol, made by the adrenal cortex, rises early
sues and attaching to receptor sites in a “lock-and-key” type of in the day, declines toward evening, and rises again toward
, CHAPTER 52 Assessment: Endocrine System 1267
TABLE 52.1 Endocrine Glands and Hormones
Hormones Target Tissue Functions
Anterior Pituitary (Adenohypophysis)
Adrenocorticotropic hormone (ACTH) Adrenal cortex Fosters growth of adrenal cortex
Stimulates corticosteroid secretion
Gonadotropic hormones Reproductive organs Stimulates sex hormone secretion, reproductive organ growth, reproductive
• Follicle-stimulating hormone (FSH) processes
• Luteinizing hormone (LH)
Growth hormone (GH), or somatotropin All body cells Promotes protein anabolism (growth, tissue repair) and lipid mobilization and
catabolism
Melanocyte-stimulating hormone (MSH) Melanocytes in skin ↑ Melanin production in melanocytes
Prolactin Ovary and mammary Stimulates milk production in lactating women. ↑ Response of follicles to LH
glands in women and FSH
Testes in men Stimulates testicular function in men
Thyroid-stimulating hormone (TSH), or thyrotropin Thyroid gland Stimulates synthesis and release of thyroid hormones, growth and function of
thyroid gland
Posterior Pituitary (Neurohypophysis)
Antidiuretic hormone (ADH) Renal tubules, vascular Promotes reabsorption of water from the renal tubules, vasoconstriction
smooth muscle
Oxytocin Uterus, mammary glands Stimulates milk secretion, uterine contractility
Thyroid
Calcitonin Bone tissue Regulates calcium and phosphorus serum levels. ↓ Serum Ca2+ levels
Thyroxine (T4) All body tissues Precursor to T3
Triiodothyronine (T3) All body tissues Regulates metabolic rate of all cells and processes of cell growth and tissue
differentiation
Parathyroids
Parathyroid hormone (PTH) or parathormone Bone, intestine, kidneys Regulates calcium and phosphorus serum levels. Promotes bone
demineralization and ↑ intestinal absorption of Ca2+. ↑ Serum Ca2+ levels
Adrenal Medulla
Epinephrine (adrenaline) Catecholamine ↑ In response to stress. Enhances and prolongs effects of sympathetic nervous
system
Norepinephrine (noradrenaline) Catecholamine ↑ In response to stress. Enhances and prolongs effects of sympathetic nervous
system
Adrenal Cortex
Androgens (e.g., dehydroepiandrosterone Reproductive organs Promotes growth spurt in adolescence, secondary sex characteristics, and libido
[DHEA], androsterone) and estradiol in both sexes
Corticosteroids (e.g., cortisol, hydrocortisone) All body tissues Promotes metabolism. ↑ In response to stress. Antiinflammatory
Mineralocorticoids (e.g., aldosterone) Kidney Regulates sodium and potassium balance and thus water balance
Pancreas (Islets of Langerhans)
Amylin (from β cells) Liver, stomach ↓ Gastric motility, glucagon secretion, and endogenous glucose release from
liver. ↑ Satiety
Glucagon (from α cells) General Stimulates glycogenolysis and gluconeogenesis
Insulin (from β cells) General Promotes glucose transport from the blood into the cell
Pancreatic polypeptide General Influences regulation of pancreatic exocrine function and metabolism of
absorbed nutrients
Somatostatin Pancreas Inhibits insulin and glucagon secretion
Gonads
Women: Ovaries
Estrogen Reproductive system, breasts Stimulates development of secondary sex characteristics, preparation of uterus
for fertilization, and fetal development. Stimulates bone growth
Progesterone Reproductive system Maintains lining of uterus needed for successful pregnancy
Men: Testes
Testosterone Reproductive system Stimulates development of secondary sex characteristics, spermatogenesis
