Endocrinology

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Medical Language, Second Edition Susan Turley

CHAPTER

Medical LanguageSecond Edition

Endocrinology

14

Endocrinology

• The medical specialty that studies the anatomy and physiology of the endocrine system and uses diagnostic tests, medical and surgical procedures, and drugs to treat endocrine system diseases.

Figure 14-1 Endocrine system

Anatomy and Physiology• The endocrine system includes:

– Hypothalamus– Pituitary gland– Pineal gland– Thyroid gland– Parathyroid glands

Anatomy and Physiology• The endocrine system includes:

– Thymus– Pancreas– Adrenal glands– Ovaries– Testes

Anatomy and Physiology (cont’d)

• All endocrine glands are alike in these ways:– They secrete substances known as hormones.– They secrete their hormones directly into the

blood and not through ducts.– Their hormones regulate specific body functions.

Anatomy and Physiology (cont’d)

• One of the functions of the endocrine system is to keep the body in homeostasis by regulating body fluids, electrolytes, glucose, cellular metabolism, growth, and the wake-sleep cycle.

Anatomy and Physiology (cont’d)

• Some endocrine glands do “double duty” as part of another body system, such as the nervous system (hypothalamus and posterior pituitary gland), immune system (thymus), the digestive system (pancreas), or the genital and reproductive system (ovaries, testes).

Anatomy of the Endocrine System

• Hypothalamus– Located in the brain just below the thalamus– Functions as part of both the nervous system and

the endocrine system– Secretes substances that stimulate or inhibit the

secretion of hormones from the anterior pituitary gland

– Produces hormones ADH and oxytocin

Figure 14-2 Endocrine glands in the brain

Anatomy of the Endocrine System (cont’d)

• Pituitary Gland– Located in the brain at the end of the stalk from

the hypothalamus– Known as the master gland of the body– Contains two different glands that function

independently of each other: the anterior pituitary gland and the posterior pituitary gland

Anatomy of the Endocrine System (cont’d)

• The anterior pituitary gland secretes seven hormones:– Thyroid-stimulating hormone (TSH)– Follicle-stimulating hormone (FSH)– Luteinizing hormone (LH)– Prolactin– Adrenocorticotropic hormone (ACTH)– Growth hormone (GH)– Melanocyte-stimulating hormone (MSH)

Figure 14-3 Hormones of the anterior and posterior pituitary gland

Anatomy of the Endocrine System (cont’d)

• The posterior pituitary gland secretes two hormones that are produced in the hypothalamus.– Antidiuretic hormone (ADH)– Oxytocin

Anatomy of the Endocrine System (cont’d)

• Pineal Gland– Located between the two lobes of the thalamus– Secretes the hormone melatonin– Maintains the body’s internal clock and regulates

the onset and duration of sleep

Anatomy of the Endocrine System (cont’d)

• Thyroid Gland– An irregularly shaped gland that has two lobes

connected by a thin bridge of tissue (the isthmus)– Located in the neck on either side of the trachea

and across its anterior surface

Anatomy of the Endocrine System (cont’d)

• The thyroid gland secretes three hormones:– T3 or triiodothyronine

– T4 or thyroxine– Calcitonin

• When the thyroid gland is functioning properly, this steady state is known as euthyroidism.

Figure 14-4 Thyroid gland and parathyroid glands

Anatomy of the Endocrine System (cont’d)

• Parathyroid Glands– Four tiny glands– Located on the posterior surface of the thyroid

gland, two on each lobe– Secrete parathyroid hormone, which regulates the

amount of calcium in the blood

Anatomy of the Endocrine System (cont’d)

• Thymus Gland– A pink gland with two lobes located in the thoracic

cavity posterior to the sternum– Large during childhood and puberty but shrinks

during adulthood– Functions as part of both the body’s immune

response and the endocrine system– Secretes thymosin

Anatomy of the Endocrine System (cont’d)

• Pancreas– A yellow, elongated, triangular gland located

posterior to the stomach– Functions as part of both the digestive system and

the endocrine system– Secretes the hormones glucagon, insulin, and

somatostatin from a group of cells known as the islets of Langerhans

Figure 14-5 Pancreas

Anatomy of the Endocrine System (cont’d)

• Adrenal Glands– Contains two different glands draped over the

superior end of each kidney.– Each gland has an outer layer (cortex) and an inner

layer (medulla).– Each layer functions independently of the other

and secretes its own hormones.

Figure 14-6 Adrenal gland

Anatomy of the Endocrine System (cont’d)

• Adrenal Cortex– Secretes three groups of hormones:

• Mineralocorticoids―Aldosterone• Glucocorticoids―Cortisol• Androgens―Male sex hormones (in the blood, some of

the androgens are changed to estrogens, female sex hormones)

Anatomy of the Endocrine System (cont’d)

• Adrenal Medulla– Secretes the hormones epinephrine and

norepinephrine into the blood when the gland is stimulated by a nerve impulse

Anatomy of the Endocrine System (cont’d)

• Ovaries– Small, egg-shaped glands located in the pelvic

cavity– Function as part of both the female reproductive

system and the endocrine system

Anatomy of the Endocrine System (cont’d)

• Ovaries– Follicles of the ovary secrete estradiol, the most

abundant and most biologically active female hormone

– The corpus luteum (ruptured ovarian follicle) secretes estradiol and progesterone.

– Cells around the follicle secrete testosterone

Anatomy of the Endocrine System (cont’d)

• Testes– Egg-shaped glands located outside the body in the

scrotum– Function as part of both the male genitourinary

system and the endocrine system– Seminiferous tubules produce spermatozoa– Secrete testosterone, the most abundant and

biologically active of all the androgens

Anatomy of the Endocrine System (cont’d)

• Physiology of Hormone Response and Feedback– The endocrine system uses hormones as chemical

messengers.– Some neurotransmitters (epinephrine and

norepinephrine) are also hormones because they are secreted by a gland and travel in the blood.

– Hormones target specific glands or organs with receptors to which they can bind.

Anatomy of the Endocrine System (cont’d)

• Synergism − When two hormones work in conjunction with one another to accomplish an enhanced effect.

• Antagonism − When two hormones exert an opposite effect.

• The endocrine system maintains body homeostasis through the use of hormones and a negative feedback mechanism.

Figure 14-7 Effects of hormones

Diseases and Conditions• Anterior Pituitary Gland: All Hormones

– Hyperpituitarism – Hypopituitarism– Dwarfism

Diseases and Conditions (cont’d)

• Anterior Pituitary Gland: Prolactin– Galactorrhea – Failure of lactation

Diseases and Conditions (cont’d)

• Anterior Pituitary Gland: Growth Hormone– Gigantism – Acromegaly– Dwarfism

Figure 14-8 GigantismCORBIS-NY

Figure 14-9 AcromegalyNMSB/Custom Medical Stock Photo, Inc.

Diseases and Conditions (cont’d)

• Posterior Pituitary Gland: Antidiuretic Hormone (ADH)– Syndrome of inappropriate ADH (SIADH) – Diabetes insipidus (DI)

Diseases and Conditions (cont’d)

• Posterior Pituitary Gland: Oxytocin– Uterine inertia– Postpartum hemorrhage

Diseases and Conditions (cont’d)

• Pineal Gland: Melatonin– Seasonal affective disorder (SAD)

Diseases and Conditions (cont’d)

• Thyroid Gland: T3 and T4 Thyroid Hormones– Hyperthyroidism

• Thyrotoxicosis• Graves’ disease

Figure 14-10 ExophthalmosCustom Medical Stock Photo, Inc.

Figure 14-11 GoiterMarka/Custom Medical Stock Photo, Inc.

Figure 14-12 Physical examination of the thyroid glandPearson Education/PH College

Diseases and Conditions (cont’d)

• Thyroid Gland: T3 and T4 Thyroid Hormones (cont’d)– Goiter or thyromegaly

Diseases and Conditions (cont’d)

• Thyroid Gland: T3 and T4 Thyroid Hormones (cont’d) – Hyperthyroidism – Hypothyroidism

Diseases and Conditions (cont’d)

• Thyroid Gland: T3 and T4 Thyroid Hormones (cont’d) – Hypothyroidism– Thyroid carcinoma– Thyroiditis

Diseases and Conditions (cont’d)

• Parathyroid Glands: Parathyroid Hormone– Hyperparathyroidism – Hypoparathyroidism

Diseases and Conditions (cont’d)

• Pancreas: Insulin– Hyperinsulinism– Insulin resistance syndrome

Diseases and Conditions (cont’d)

• Pancreas: Insulin (cont’d)– Diabetes Mellitus (DM)– Ketoacidosis

Table 14-1 Diabetes Mellitus

Diseases and Conditions (cont’d)

• Adrenal Cortex: Aldosterone– Hyperaldosteronism – Hypoaldosteronism

Diseases and Conditions (cont’d)

• Adrenal Cortex: Cortisol– Cushing’s syndrome– Addison’s disease

Figure 14-13 Cushing’s syndrome(a) Biophoto Associates / Science Source / Photo Researchers, Inc.

Diseases and Conditions (cont’d)

• Adrenal Cortex: Androgens– Adrenogenital syndrome

Diseases and Conditions (cont’d)

• Adrenal Medulla: Epinephrine and Norepinephrine– Pheochromocytoma

Diseases and Conditions (cont’d)

• Ovaries: Estradiol and Progesterone– Precocious puberty – Infertility– Menopause

Diseases and Conditions (cont’d)

• Testes: Testosterone– Precocious puberty – Gynecomastia– Infertility

Laboratory and Diagnostic Procedures

• Blood Tests– Antithyroglobulin antibodies – Calcium– Cortisol level

Laboratory and Diagnostic Procedures (cont’d)

• Blood Tests (cont’d) – Fasting blood sugar (FBS)– FSH assay and LH assay – Glucose self-testing

Figure 14-14 Blood glucose monitorPearson Education/PH College

Laboratory and Diagnostic Procedures (cont’d)

• Blood Tests (cont’d) – Glucose tolerance test (GTT) – Growth hormone

• Blood Tests (cont’d) – Hemoglobin A1c (HbA1c) – Testosterone– Thyroid function tests (TFTs)

Laboratory and Diagnostic Procedures (cont’d)

• Urine Tests– ADH stimulation test – Estradiol– Urine dipstick– Vanillylmandelic acid (VMA)

Laboratory and Diagnostic Procedures (cont’d)

• Radiology Tests– Radioactive iodine uptake (RAIU) and thyroid scan

Laboratory and Diagnostic Procedures (cont’d)

Figure 14-15 Thyroid scanCustom Medical Stock Photo, Inc.

Medical and Surgical Procedures

• Medical Procedures– ADA diet

Medical and Surgical Procedures (cont’d)

• Surgical Procedures– Adrenalectomy – Fine-needle biopsy

Medical and Surgical Procedures (cont’d)

• Surgical Procedures (cont’d) – Parathyroidectomy – Thymectomy– Thyroidectomy – Transsphenoidal hypophysectomy

Drug Categories

• These categories of drugs are used to treat endocrine Diseases and Conditions:– Antidiabetic drugs– Antithyroid drugs– Corticosteroid drugs– Growth hormone drugs– Insulin– Thyroid supplement drugs

Figure 14-16 Insulin injectionCustom Medical Stock Photo, Inc.

Figure 14-17 Humulin R insulinSIU BioMed/Custom Medical Stock Photo, Inc.

Abbreviations