Endocrine System Part II

Flow Chart for Thyroxine Hypothalamus produces TRH TRH targets the anterior pituitary Anterior pituitary produces TSH TSH targets the thyroid gland Thyroid gland produces thyroxine

TRH and TSH Feedback Mechanism

Flow Chart for Adrenal Cortex Hormones Hypothalamus produces CRH CRH targets the anterior pituitary Anterior pituitary produces ACTH ACTH targets the adrenal gland Adrenal gland produces hormones

CRH and ACTH Feedback Mechanism

Flow Chart for Gonadal Hormones Hypothalamus produces GnRH GnRH targets the anterior pituitary Anterior pituitary produces FSH and LH FSH/LH targets the gonads (ovaries/testes) Gonads produces hormones, sex cells, etc.

Flow Chart for Prolactin Hypothalamus produces PRH PRH targets the anterior pituitary Anterior pituitary produces PRL PRL targets the mammary glands (breast) Mammary glands produces milk

Flow Chart for Prolactin Hypothalamus produces PIH PIH targets the anterior pituitary Anterior pituitary slows production of PRL X Mammary glands do not produce milk

Target Organ of Prolactin

Prolactin “Wet nurses” Breast stimulation in full-term pregnancy Male lactation

Review Questions What is the target organ of TSH? What is the function of TSH? What hormone promotes the secretion of TSH?

Review Questions What is the target organ of ACTH? What is the function of ACTH? What hormone promotes the secretion of ACTH?

Review Questions What is the target organ of PRL? What is the target organ of PIH? Which hormone is normally in control of PRL release in non-lactating humans? Which hormone promotes PRL release in a breast-feeding female?

Review Questions Identify the hormone that: _____ Stimulates TSH production _____ Decreases prolactin levels _____ Promotes growth of skeletal muscles & bones _____ Stimulates the release of ACTH _____ Inhibits release of GH _____ Stimulates the release of FSH and LH _____ Promotes uterine contractions

Review Questions Which of these hormones is made by the hypothalamus (check all that apply): _____ TSH _____ GH _____ Oxytocin _____ CRH _____ ACTH _____ Prolactin

Posterior Pituitary Gland

Oxytocin Target organs: Uterus and mammary glands Functions – Smooth muscle contractions in the uterus of a female – Contraction of cells in the mammary glands to promote the milk letdown or milk reflex – Any function in males?

Antidiuretic Hormone (ADH) Also known as Vasopressin Target organ: kidney Functions – Promotes water retention – Prevents dehydration – Increases blood pressure through vasoconstriction Produced in response to high blood concentration of solutes (called osmotic pressure) What effect does alcohol have on ADH production?

Diabetes Insipidus The “Other” Diabetes Cause: Hyposecretion of ADH Signs/symptoms: Polyuria, polydipsia More info at:

Thyroid and Parathyroid Glands

Thyroid Follicles & Colloid Colloid Follicle cells

Thyroid Follicles Make Thryroid Hormones Notice thyroxine can be stored (for around 30 days!)

Thyroid Gland Hormones “Thyroid Hormone” (TH) is actually two hormones: – Thyroxine or T 4 – Triiodothyronine or T 3 Calcitonin

T 3 and T 4 T 3 and T 4 differ only by 1 iodine atom

Flow Chart for Thyroxine Hypothalamus produces TRH TRH targets the anterior pituitary Anterior pituitary produces TSH TSH targets the thyroid gland Thyroid gland produces thyroxine

Thyroid Hormone (TH)‏ Functions: – Regulation of metabolism – Regulation of development

TH = Thyroxine or T 4 T 4 is released by thyroid follicles...it travels to cells of the body (via a transport protein called thyroglobulin in the blood)‏ In the cells, T 4 is converted to T 3 (more potent but less common thyroid hormone)‏

Calcitonin Produced by the parafollicular cells of the thyroid gland

Calcitonin Target organ: bones Function: Lowers blood calcium by depositing calcium to the bones

Calcitonin Calcitonin is stimulated when blood calcium levels are too high. – Is this humoral, hormonal, or neural stimulation?

Thyroid Gland Disorders

Hypothyroidism = insufficient TH – Myxedema – Cretinism (Congenital Hypothyroidism) – Goiter Hyperthyroidism = excess TH – Graves disease – Goiter

Thyroid Gland Disorders Cretinism; Congenital hypothyroidism – Affects children – Caused by insufficient thyroxine – Signs/Symptoms: Underdeveloped body, weak muscles and bones, thick skin, mental retardation. – Newborns are screened for thyroid levels.

Cretinism (Congenital Hypothyroidism)

Cretinism Congenital Hypothyroidism Affects babies/ children Girl before treatment 16 years old

Cretinism After Treatment with Thyroxine 18 years old

Far Left: Cretinism, hypothyroidism (notice disproportionate body) Next two, Pituitary Dwarfs (notice proportions are correct) Next two could be achondroplasic dwarfs (notice disproportionate size of extremities)‏

Thyroid Gland Disorders Myxedema – Affects adults – Caused by severe, untreated hypothyroidism (too little thyroxine). – Signs/symptoms include hair loss, dry skin, fatigue, can't think clearly, slow heart rate, weight gain

Myxedema Results from Hypothyroidism

Thyroid Gland Disorders Goiter – Enlargement of the thyroid gland results from lack of iodine or an iodine metabolism problem. – Why does the thyroid gland enlarge? Iodine is collected from blood. The thyroid gland enlarges because not enough iodine can be concentrated to make thyroxine.

Goiter Belt Inadequate iodine in soil and water

Proper thyroid functioning requires iodine

Thyroid Gland Disorders Iodine deficiency promotes a form of hypothyroidism known as goiter Goiter Treatments – Iodine (found in salt due to “goiter belt”)‏ – Thyroid hormone (such as Levothyroid, Synthroid) – Surgery to remove the thyroid gland – Radioactive iodine (to “kill” the thyroid gland)

Endemic Goiter Lack of Iodine

Hyperthyroidism & Graves Disease

Graves Graves Disease – Caused by hyperthyroidism (too much thyroxine). – Signs/Symptoms: Difficulty sleeping, fast heart rate, weight loss, heat insensitive – Associated problem – a bulging eye condition known as exophthalmus

Graves Disease Hyperthyroidism Notice bulging eyes, called exophthalmus —a typical symptom

Exophthalmus

Symptoms of Graves rapid heart beat weight loss without dieting heat sensitivity increased perspiration fine or brittle hair insomnia irritability muscular weakness lighter menstrual flow hand tremors

Parathyroid Glands

One hormone is made: Parathyroid hormone (PTH)

PTH Function – Increase blood calcium levels Production occurs in response to low blood calcium levels (humoral control) How does breastfeeding affect PTH production? What hormone acts as an antagonist to PTH?

Three Target Organs of PTH Bone: Stimulates osteoclasts to break down bone matrix and release calcium Kidneys: Promotes increased absorption of calcium back into the blood Intestines: Promotes increased reabsorption of calcium through intestinal mucosa

Notice the dark spots for the parathyroid glands indicating hyperparathyroidism

Hyperparathyroidism Signs and Symptoms Stones Bones Groans Moans

Hyperparathyroidism Signs/Symptoms

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