Chap 40 Mechanisms of Endocrine Control

While reviewing the major actions of follicle-stimulating hormone (FSH), the faculty points out that in males this hormone is responsible for the:

sperm production. Explanation: FSH in males stimulates sperm production. GH stimulates growth of bone and muscle. LH stimulates secretions of testosterone. Androgens affect the development of male sex organs.

When discussing luteinizing hormone and follicle-stimulating hormone with students, the instructor will emphasize that these hormones are under the control of:

Anterior pituitary gland Explanation: The pituitary gland has been called the master gland because its hormones control the functions of many target glands and cells. The anterior pituitary gland or adenohypophysis contains five cell types: (1) thyrotrophs, which produce thyrotropin, also called TSH; (2) corticotrophs, which produce corticotropin, also called ACTH; (3) gonadotrophs, which produce the gonadotropins, LH, and FSH; (4) somatotrophs, which produce GH; and (5) lactotrophs, which produce prolactin.

A client experiences an increase in thyroid hormone as a result of a thyroid tumor. Which hormonal response demonstrates the negative feedback mechanism?

Decreased thyroid-stimulating hormone (TSH) Explanation: Negative feedback occurs when secretion of one hormone causes a reduction in the secretion of the hormone that stimulates production of the first hormone. In this case, TSH, which is manufactured by the anterior pituitary gland, would normally stimulate release of thyroid hormones, but with the increase of those hormones by the secreting tumor, enough thyroid hormones flood the system that there should be a reduction in TSH levels.

When hypofunction of an endocrine organ is suspected, which type of diagnostic test can be administered to measure and assess target gland response?

Hormone stimulation Explanation: Stimulating hormone can be given to identify (determine hypofunction) if the target gland is able to increase hormone response to increased stimulation. Agglutination with enzymes is a way of measuring hormone antigen levels. The 24-hour urine sample measures hormone metabolite excretion. Radioactive hormone-antibody binding levels provide a method of measuring plasma levels.

While teaching a science class, the instructor mentions that both autocrine and paracrine hormonal actions occur without entering the bloodstream. A student aks, "What cells do paracrine actions affect?" Which response is correct?

Local Explanation: Paracrine actions are hormonal interactions with local cells other than those that produce the hormone; autocrine actions are with self-cells (cells from which they were produced). Both autocrine and paracrine hormonal actions affect target cells. Neither paracrine nor autocrine actions affect cell storage.

As part of maintaining homeostasis, why are hormones, secreted by endocrine cells, continuously inactivated?

Prevent accumulation Explanation: Continuous inactivation of secreted hormones is necessary to prevent accumulation that could disrupt the feedback mechanism. Increased secretion stimulates production of more receptor sites. Metabolic waste absorption is not a function of the endocrine system.

A client with a history of brain tumors that resulted in partial removal of the pituitary gland years ago expresses concern to the health care provider about whether she will be able to breast-feed her infant. Which physiologic function of the pituitary gland facilitates breast milk production?

Prolactin Explanation: The anterior pituitary gland or adenohypophysis contains five cell types: (1) thyrotrophs, which produce thyrotropin, also called TSH; (2) corticotrophs, which produce corticotropin, also called ACTH; (3) gonadotrophs, which produce the gonadotropins, LH and FSH; (4) somatotrophs, which produce GH; and (5) lactotrophs, which produce prolactin that is involved with breast growth and milk production.

A client has received an injection containing thyrotropin-releasing hormone (TRH) and is now being assessed for serum levels of thyroid-stimulating hormone (TSH). Which type of diagnostic testing is this client undergoing?

Stimulation testing Explanation: Introduction of TRH tests the pituitary gland's ability to produce TSH, and is an example of a stimulation test. Suppression testing examines a gland's response to a stimulus that would normally result in decreased hormone production. RIA and autoantibody testing are examples of direct and indirect measurement of serum levels of a hormone.

A client with many nonspecific complaints has been ordered a positron emission tomography (PET) scanning for evaluation of:

tumors located on the endocrine glands. Explanation: Positron emission tomography (PET) scanning is being used more widely for evaluation of endocrine tumors. PET scans do not calculate the pancreas response to insulin. A DEXA is used for diagnosis and monitoring of osteoporosis (bone density). Isotopic imaging includes radioactive scanning of the thyroid (using radioiodine) and parathyroids.

In major athletic competition, athletes are required to submit to liquid chromatography testing looking for:

use of performance-enhancing agents to increase the chances of winning. Explanation: For some steroid or peptide hormones, mass spectrometry is becoming increasingly useful and can be combined with other analytical techniques, such as liquid chromatography. These approaches provide definitive identification of the relevant hormone or compound according to its chemical or physical characteristics (e.g., unequivocal detection of performance-enhancing agents in sports).

A client has developed a tumor of the posterior pituitary gland. The client is at risk for problems with secretions of:

Antidiuretic hormone (ADH) and oxytocin Explanation: The posterior pituitary secretes ADH and oxytocin/vasopressin, while the anterior pituitary secretes the hormones listed in the other choices.

The release of insulin from the pancreatic beta cells can inhibit further release of insulin from the same cells. This is an example of which type of hormone action?

Autocrine Explanation: Hormones can exert autocrine action on the cells from which they were produced. Retinoids are compounds with hormone-like actions. Juxtacrine action involves a chemical messenger imbedded in a plasma membrane that interacts with a specific receptor on a juxtaposed cell. Arachidonic acid is a precursor for eicosanoid compounds (similar to retinoids).

Which hormone is produced by the anterior pituitary gland?

Growth hormone (GH) Explanation: GH is among the hormones produced and released by the anterior pituitary. Oxytocin is a posterior pituitary hormone, whereas CRH is produced by the hypothalamus. Norepinephrine and epinephrine are produced by the adrenal medulla.

An infant whose mother had myxedema during the pregnancy has failed to meet standards for growth and is developmentally delayed. Which hormonal imbalance is this child exhibiting?

Hypothyroidism Explanation: Thyroid hormone is necessary for metabolism at all ages, as well as growth and development during childhood. Uncorrected thyroid insufficiency in childhood leads to cretinism, a condition with marked physical and intellectual disability. Myxedema is the term used for thyroid insufficiency in adults.

A nurse who works in the office of an endocrinologist is orienting a new staff member. Which teaching point should the nurse include in the orientation?

"A single hormone can act on not only one process or organ but often on several different locations or processes." Explanation: A single hormone can exert various effects in different tissues, or conversely, a single function can be regulated by several different hormones. Hormones act both distantly from their source and more locally, as in the case of autocrine and paracrine actions. Hormones are normally present at all times.

While discussing the regulation of hormone levels, the instructor gives an example of hormones regulated by feedback mechanisms. Which example of this regulation is best?

Following a meal that was high in carbohydrates, a person's blood glucose elevates, which stimulates the release of insulin from the pancreas. Explanation: The levels of hormones such as insulin and antidiuretic hormone (ADH) are regulated by feedback mechanisms that monitor substances such as glucose (insulin) and water (ADH) in the body. None of the other examples are accurate examples of this feedback mechanism.

Which physiologic process allows hormones to exert influence upon some cells and not others?

Hormone receptors Explanation: Hormone receptors are complex molecular structures (usually proteins) that are located either on the cell surface or inside target cells. The structure of these receptors is specific to a particular hormone, which allows target cells to respond to one hormone and not to others. For example, receptors in the thyroid are specific for thyroid-stimulating hormone, and receptors on the gonads respond to the gonadotropic hormones. Positive feedback control occurs when rising levels of a hormone cause another gland to release a hormone that is stimulating to the first. Protein binding describes the ability of proteins to form bonds with other substances. Pituitary-hypothalamic feedback describes negative feedback.

The hormone levels in the body need to be kept within an appropriate range. How is this accomplished for many of the hormones in the body?

Negative feedback loop Explanation: The level of many of the hormones in the body is regulated by negative feedback mechanisms.

A teen with newly diagnosed pituitary dwarfism asks the nurse why growth hormone must be taken as an injection rather than a pill like the steroids used for arthritis. Which response best answers the client's question?

Peptide proteins will be digested instead of entering the bloodstream. Explanation: Although each of the foregoing statements about hormones is true, only one directly answers the client's question. Hormones can be placed into three categories according to structure: Amines and amino acids are the first group and include norepinephrine, epinephrine, and the thyroid hormones. The second group contains most of the hormones and consists of peptides and proteins. The third group is steroids that are made from cholesterol. These hormones are not degraded by the gastrointestinal enzymes. Growth hormone is a large protein in the class of peptides and proteins—the group with bonds that can be digested in the gastrointestinal tract.

Which gland is often referred to as the master gland because it secretes many hormones?

Pituitary Explanation: The pituitary gland has been called the master gland because its hormones control the functions of many target glands and cells. That is not a term used to refer to the other options.

Which structure controls the functions of the greatest number of target glands and cells?

Pituitary gland Explanation: The pituitary gland has been called the master gland because its hormones control the functions of many target glands and cells. It supersedes the importance of the thyroid, adrenal cortex, or pancreas in this regulatory role.

Hormones are chemical messengers that provide which function in the body?

Regulate body functions Explanation: Hormones regulate and integrate body functions. Hormones act on specific target cells, but they cause a variety of effects on tissues. Hormones do not transport other substances; hormones are transported and present in body fluids at all times.

When explaining factors that influence the number of receptors present on target cells, the instructor will likely mention which concepts? Select all that apply.

The role antibodies may have on receptor proteins. A decreased hormone level may produce increased receptor numbers. A sustained excess hormone level brings about a decrease in receptor numbers. Explanation: Target cell response varies with the number and affinity of the relevant receptors. The number of hormone receptors on a cell may be altered for any of several reasons. Antibodies may destroy or block the receptor proteins. Increased or decreased hormone levels often induce changes in the activity of the genes that regulate receptor synthesis. For example, decreased hormone levels often produce an increase in receptor numbers by means of a process called up-regulation; this increases the sensitivity of the body to existing hormone levels. Likewise, sustained levels of excess hormone often bring about a decrease in receptor numbers by down-regulation, producing a decrease in hormone sensitivity.

The vesicle-mediated pathway has a role in synthesis and release of which hormones? Select all that apply.

Dopamine Follicle-stimulating hormone Antidiuretic hormone Explanation: The protein hormones and some of the nonpolypeptide hormones, such as dopamine, epinephrine, and norepinephrine, use the vesicle-mediated pathway. Steroids use the non-vesicle-mediated pathway.

Which type of imaging is preferred to evaluate the bone density of a client with hyperparathyroidism?

Dual energy x-ray absorptiometry (DXA) scan Explanation: Preferred types of scans for endocrine tissues include MRI of the pituitary gland and hypothalamus, CT scan of the adrenal glands, DXA scan of bone density, and ultrasound of possible nodules of the thyroid gland. Bone density may be decreased in a client with hyperparathyroidism.

Which gland acts as a signal-relaying bridge between multiple body systems and the pituitary gland?

Hypothalamus Explanation: The activity of the hypothalamus is regulated by both hormonally mediated signals (e.g., negative feedback signals) and by neuronal input from a number of sources. Neuronal signals are mediated by neurotransmitters such as acetylcholine, dopamine, norepinephrine, serotonin, gamm-aminobutyric acid (GABA), and opioids. Cytokines that are involved in immune and inflammatory responses, such as the interleukins, also are involved in the regulation of hypothalamic function. This is particularly true of the hormones involved in the hypothalamic-pituitary-adrenal axis. Thus, the hypothalamus can be viewed as a bridge by which signals from multiple systems are relayed to the pituitary gland. This cannot be said of the other options.

A health care provider is assessing a client for a potential endocrine disorder. Assessment findings identify abnormalities with emotion, pain, and body temperature. Which mechanism of endocrine control will require further laboratory/diagnostic assessment?

Hypothalamus Explanation: The hypothalamus is the coordinating center of the brain for endocrine, behavioral, and autonomic nervous system function. It is at the level of the hypothalamus that emotion, pain, body temperature, and other neural input are communicated to the endocrine system. The anterior pituitary regulates several physiologic processes, including stress, growth, reproduction, and lactation. The cerebellum is involved in motor control, and the cerebral cortex is associated with sensory, motor, and association.

A nursing instructor is teaching a group of students about the action of hormones. The instructor determined that teaching was effective when the students recognize the local action of hormones as:

Paracrine Explanation: When hormones act locally on cells other than those that produced the hormone, the action is called paracrine. Hormones can also exert an autocrine action on the cells in which they were produced. Pancreatic and hormonal are not actions.

A client undergoing an evaluation of hormone levels asks, "What regulates the hormone levels?" Which response by the nurse would be considered most accurate?

The hypothalamic-pituitary-target cell system Explanation: The levels of many of the hormones are regulated by feedback mechanisms that involve the hypothalamic-pituitary-target cell system. Positive feedback control refers to rising levels of a hormone that causes another gland to release a hormone that is stimulating to the first. The hypophyseal portal system connects the supraoptic and paraventricular nuclei of the hypothalamus with the posterior pituitary gland. Exogenous forms of hormones (given as drug preparations) can influence the normal feedback control of hormone production and release.

The nurse is teaching a client who has been newly diagnosed with hypothyroidism about the function of the thyroid. Which statement about the role of the thyroid gland is most accurate?

The thyroid gland is responsible for increasing the metabolic rate. Explanation: The thyroid gland produces thyroid hormones, T3 and T4. These hormones increase the metabolic rate; increase protein and bone turnover; increase responsiveness to catecholamines; are necessary for fetal and infant growth and development. The parathyroid gland regulates calcium metabolism. The adrenal glands regulate "flight or fight" and the testes or ovaries regulate development of secondary sex characteristics