Chapter 32 Disorders of Endocrine Control of Growth and Metabolism

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins

Chapter 32

Disorders of Endocrine Control of Growth and Metabolism

Chapter 32

Disorders of Endocrine Control of Growth and Metabolism


Hypothalamus- Pituitary AxisHypothalamus- Pituitary Axis

• Releasing hormones from hypothalamus tell the pituitary what to release into the blood

• Trophic hormones from the pituitary tell specific peripheral glands to grow and produce their hormones


Primary: abnormality in the gland

Secondary: abnormality in stimulation from the pituitary

Tertiary: abnormality in stimulation from the hypothalamus

Hormone DisordersHormone Disorders


Growth hormone

FSH and LH

ACTHTSH

stimulate gonads

stimulates thyroid

stimulates adrenal cortex

Pituitary HormonesPituitary

Hormones


Question Question

Which hormone(s) is/are secreted by the ovaries and testes?

a. GH

b. FSH & LH

c. TSH

d. ACTH & GH


Answer Answer

b. FSH & LH

Gonads are sex organs (ovaries and testes). These organs secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH).


The Hypothalamus Controls Growth Hormone ReleaseThe Hypothalamus Controls Growth Hormone Release

• GH secretion stimulated by:

– Hypoglycemia, fasting, starvation

– Stress

• GH inhibited by:

– Increased glucose levels, free fatty acid release, and obesity

– Cortisol

GHRH stimulates

Somatostatin inhibits

Hypothalamus

Anterior pituitary

Growth hormone


Functions of Growth HormoneFunctions of Growth Hormone


Growth Hormone DeficiencyGrowth Hormone Deficiency

• Idiopathic GH deficiency

– Lacks hypothalamic GHRH

• Pituitary tumors, agenesis of the pituitary

– Cannot produce GH

• Laron-type dwarfism

– Hereditary defect in IGF production


Growth Hormone ExcessGrowth Hormone Excess

• In childhood: gigantism

• In adulthood: acromegaly


Question Question

Tell whether the following statement is true or false:

GH deficiency may result in dwarfism.


Answer Answer

True

Laron-type dwarfism is caused by a genetic inability to produce normal amounts of GH.


The Hypothalamus Controls Gonadal Hormone ReleaseThe Hypothalamus Controls Gonadal Hormone Release

• Excessive GnRH secretion can be stimulated by:

– Hypothalamus tumors

– Pituitary tumors

• Giving high levels of GnRH causes the pituitary to become less responsive and reduces the effects of abnormal GnRH secretion

GnRH stimulates

Hypothalamus

anterior pituitary

FSH

production of gametes and gonadal hormones

LH


Thyroid ControlThyroid Control

• Thyroid releases T3 and T4

• Both are carried by binding proteins

• T3 stimulates metabolism

• T4 is inactive until converted into T3 in the tissues

• Both exert negative feedback on the hypothalamus


Thyroid Insufficiency Due to Lack of I-Thyroid Insufficiency Due to Lack of I-

• T3 and T4 are not made

• There is no negative feedback to the hypothalamus

• TRH and TSH continue to be made

• If it is able, the thyroid will grow in response to the TSH


Thyroid ImbalancesThyroid Imbalances

• Hypothyroidism

– Congenital

– Acquired

º Hashimoto thyroiditis

º Thyroidectomy

• Hyperthyroidism (thyrotoxicosis)

– Graves disease

– Thyroid tumors


Question Question

Tell whether the following statement is true or false:

Simple goiter is caused by increased production of thyroid hormone.


Answer Answer

False

Simple goiter is the result of iodine (I) insufficiency. Since I is necessary in order to produce thyroid hormone, a deficiency results in low serum levels of T3/T4. This causes TSH to stimulate the thyroid gland to make more hormone (which it cannot do because it needs I). The cells of the thyroid gland hypertrophy in an effort to function (make thyroid hormone).


Major Adrenal Cortical HormonesMajor Adrenal Cortical Hormones


Actions of CortisolActions of Cortisol

cortisol

catabolism increased

blood glucoseincreased

muscle breakdown

plasma proteins

increased

free fatty acids

increased

SNS responseincreased

immune/inflammatory

systemssuppressed


Adrenal Cortical DisordersAdrenal Cortical Disorders

• Adrenal cortical insufficiency: inability to make all 3 hormones

– Primary adrenal cortical insufficiency (Addison disease)

– Secondary adrenal cortical insufficiency

– Acute adrenal crisis

• Excessive adrenal secretion

– Glucocorticoid hormone excess (Cushing syndrome)

– Hyperaldosteronism

• Congenital adrenal hyperplasia

– Decreased cortisol synthesis; other hormones may be increased or decreased


Clinical Manifestations of Addison DiseaseClinical Manifestations of Addison Disease


Clinical Manifestations of Cushing SyndromeClinical Manifestations of Cushing Syndrome


ScenarioScenarioThree men have adrenal problems…

• One has hypoaldosteronism, one has an inability to make cortisol, and one has an inability to make testosterone.

Question

• Which of them is most likely to develop:

• Hypotension?

• High CRH levels?

• Hypoglycemia?

• Hypervirilization?

• Decreased libido?

• Hyperkalemia?


ScenarioScenario

Two women have benign pituitary tumors…

• One woman has lost weight and complains of being hot all the time; she presents as thin and nervous, with tachycardia and exophthalmos

• The second woman has gained weight in her abdomen and presents with a round face and thin arms and legs with stretch marks; she says that at her last checkup her doctor told her she was pre-diabetic

Question

• What hormones are being secreted by the pituitary tumors in these patients? Why?

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Chapter 32 Disorders of Endocrine Control of Growth and Metabolism