Page 681 - Fundamentals of anatomy physiology

668 Unit 3 Control and Regulation

Clinical Note Secondary disorders are due to problems in other organs
or target tissues. Such disorders often involve the hypothala-
Endocrine Disorders Regulation of hormone levels often mus or pituitary gland. For example, secondary hypothyroid-
involves negative feedback control mechanisms. These ism occurs when the hypothalamus or pituitary gland doesn’t
mechanisms involve the endocrine organ, neural regulatory produce enough TRH and/or TSH.
factors, and the target tissues. Hormone overproduction
­(hypersecretion) or underproduction (hyposecretion) may Abnormalities in target cells can affect their sensitivity
cause problems. Abnormal cellular sensitivity to the hormone or responsiveness to a particular hormone. For example, Type
can also lead to problems. 2 diabetes is due to the target cells’ decreased sensitivity to
insulin.
Primary disorders arise from problems within the endo-
crine organ. The underlying cause may be a metabolic factor. Endocrine disorders often reflect either abnormal
Hypothyroidism due to a lack of dietary iodine is an example. hormone production or abnormal cellular sensitivity to hor-
An endocrine organ may also malfunction due to physical mones. The signs and symptoms highlight the significance of
damage that destroys cells or disrupts the normal blood sup- normally “silent” hormonal contributions. The characteristics
ply. Congenital problems may also affect the regulation, pro- of these disorders are summarized in Table 18–8.
duction, or release of hormones by endocrine cells.

Table 18–8 Clinical Implications of Endocrine Malfunctions

18 Hormone Underproduction or Principal Signs and Symptoms Overproduction or Principal Signs and Symptoms
Growth hormone (GH) Tissue Insensitivity Retarded growth, abnormal fat Tissue Hypersensitivity Excessive growth
Pituitary growth distribution, low blood glucose Gigantism, acromegaly
Antidiuretic failure hours after a meal Increased body weight and water
hormone (ADH) Diabetes insipidus Polyuria, dehydration, thirst SIADH (syndrome of content
or vasopressin (VP) inappropriate ADH
Thyroxine (T4), Hypothyroidism, Low metabolic rate; low body secretion) High metabolic rate and body
triiodothyronine (T3) infantile temperature; impaired physical and Hyperthyroidism, Graves temperature
hypothyroidism, mental development disease
Parathyroid hormone myxedema Neurological, mental, muscular
(PTH) Hypoparathyroidism Muscular weakness, neurological Hyperparathyroidism problems due to high blood Ca2+
problems, formation of dense concentrations; weak and brittle
Insulin Diabetes mellitus bones, tetany due to low blood Excess insulin production bones
(Type 1) Ca2+ concentrations or administration Low blood glucose levels, possibly
Mineralocorticoids Hypoaldosteronism High blood glucose, impaired Aldosteronism causing coma
(MCs) glucose utilization, dependence on
Glucocorticoids (GCs) Addison’s disease lipids for energy; glycosuria Cushing’s disease Increased body weight due to Na+
Polyuria, low blood volume, and water retention; low blood K+
Epinephrine (E), None identified high blood K+, low blood Pheochromocytoma concentration
norepinephrine (NE) Na+concentrations Excessive breakdown of tissue
Inability to tolerate stress, mobilize Adrenogenital syndrome proteins and lipid reserves;
energy reserves, or maintain normal impaired glucose metabolism
blood glucose concentrations Precocious puberty High metabolic rate, body
Adrenogenital syndrome temperature, and heart rate;
(gynecomastia) elevated blood glucose levels
Estrogens (females) Hypogonadism Sterility, lack of secondary sex Overproduction of androgens by
characteristics Precocious puberty zona reticularis of adrenal cortex
leads to masculinization
Premature sexual maturation and
related behavioral changes
Androgens (males) Hypogonadism Sterility, lack of secondary sex Abnormal production of estrogen,
characteristics sometimes due to adrenal or
interstitial cell tumors; leads to
breast enlargement
Premature sexual maturation and
related behavioral changes