Thymus, Pineal, Thyroid, Parathyroids

The Thymus Location: upper thorax, posterior to sternum Description: Large in infants/children Decreases in size throughout adulthood Made of fibrous connective tissue and fat http://upload.wikimedia.org/wikipedia/commons/c/cf/Illu_thymus.jpg http://www.hormone.org/~/media/Hormone/Images/Endo%20101/Thymus.jpg?h=310&w=200

Thymosin Main hormone of the thymus Essential for development of T-cells (a group of white blood cells) and immune response http://upload.wikimedia.org/wikipedia/commons/e/ee/Thymosin_1HJ0.png

The Pineal Gland Location: brain (roof of 3rd ventricle) Description: Small, cone-shaped gland Not a lot is known about it beyond the secretion of melatonin http://upload.wikimedia.org/wikipedia/commons/4/43/Pituitary_pineal_glands.jpg

Melatonin Main hormone of the pineal Peak levels at night- drowsiness Lowest levels around noon In animals, also helps regulate mating behavior and rhythms http://upload.wikimedia.org/wikipedia/commons/4/44/Walgreens_Melatonin-2010-20-07.jpg

Seasonal Affective Disorder Type of depression Related to changes in seasons May occur due to drops in serotonin (reduced sunlight) and affect melatonin (sleep patterns, mood) Begins and ends about the same time each year (fall/winter) Saps energy, moodiness Treatment: light therapy, psychotherapy, medication

Summary- be ready to answer! Match the location of each gland. Hypothalamus Above pituitary Pituitary 3rd ventricle Thymus Sella turcica Pineal Thorax

Summary- be ready to answer! Match the function of each hormone. LH Melatonin OXT PRL Thymosin TSH Mammary gland development and lactation Plays a major part in the immune response Plays a role in sleep-wake cycles Tells the thyroid to make thyroid hormones Induces ovulation and the release of other hormones For bonding, promoting labor, and milk ejection

Summary- be ready to answer! Match the function of each hormone. ACTH ADH FSH GH GH-IH ICSH Inhibits urine production Prevents secretion of growth hormone In males, stimulates androgen production Makes adrenal cortices release hormones In females, induces follicle & egg development Maintenance and repair of body tissues

Thyroid Gland Location: in the neck Description: Base of throat, inferior to Adam’s apple Description: Two lobes joined by an isthmus Composed of follicles Regulates metabolism Influences mental & physical abilities For normal growth (along with GH) Requires iodine

Thyroid Hormone Controls the rate at which glucose is oxidized (“burned”) and converted into heat and energy Every cell in the body is a target cell

Thyroid Hormone 2 similar, iodine-containing hormones Thyroxine (T4)- major thyroid hormone Triiodothyronine (T3)- most formed at target tissues when T4 is converted to T3 Made and stored in follicles Constructed from two tyrosine amino acids linked together plus bound iodine (T3=3; T4=4)

Calcitonin Decreases blood calcium levels (deposits the calcium in bones) Is the antagonist of parathyroid hormone Made by parafollicular cells (connective tissues between follicles)

Abnormal Growths Nodule- any abnormal growth that forms a lump Goiter- enlargement of the thyroid Results from iodine deficiency Can also result from overproduction of hormones

Goiter

CRETINISM: hyposecretion of thyroxine in early childhood Lack of physical growth Lack of mental development If caught early, hormone replacement can prevent mental retardation and some other symptoms

MYXEDEMA: hyposecretion of thyroxine as adult Physical and mental sluggishness Puffiness of the face, obesity Fatigue, poor muscle tone, low body temperature Treat with oral thyroxine

HASHIMOTO’S DISEASE: autoimmune hypothyroidism Autoimmune thyroiditis- immune system attacks the thyroid May result in goiter Treat with hormone replacement, surgery

HYPERTHYROIDISM Overactive thyroid Metabolism increases, weight loss Rapid pulse, tremors, sweating, anxiety Treat with thyroid-blocking drugs, radioactive iodine to kill thyroid cells, or surgical removal of part of the thyroid

HYPERTHYROIDISM GRAVE’S DISEASE: autoimmune hyperthyroidism Symptoms of hyperthyroidism Thyroid enlarges Eyes may bulge or protrude anteriorly (exophthalmos)

THYROID CANCER Papillary: most common (70-80% of cases). Usually diagnosed age 30-50 Occurs 3x more often in women Least aggressive type May spread, but usually not beyond the neck

THYROID CANCER Follicular: 10-15% of cases Women 3x more Usually diagnosed between ages 40-60 Cancer cells may invade blood vessels and travel Can be more aggressive in older patients

THYROID CANCER Medullary: 5-10% of all cancer cases Tends to run in families Often diagnosed ages 40-50 Males/females affected equally Develops in parafollicular cells; elevated calcitonin levels can indicate cancer

THYROID CANCER Anaplastic (rare- fewer than 5% of all cases) Generally in older people (over the age 65) Females affected more often than males Aggressive and invasive Very difficult to treat

Thyroid Neck Check https://www.youtube.com/watch?v=-kfsG7p1hSk (start at 0:29)

Parathyroid Glands Location: Posterior surface of thyroid gland (embedded) Description: Four tiny masses of glandular tissue Regulate blood calcium homeostasis

Parathyroid Hormone (PTH) or parathormone Released when blood calcium (Ca+2) levels drop Major target tissue: bone Stimulates osteoclasts to break down bone matrix and release Ca+2 into blood Also stimulates kidneys and intestine to absorb more Ca+2

Parathyroid Hormone Diseases TETANY: uncontrollable muscle spasms due to hypocalcemia (makes neurons irritable and overactive) May be fatal

Parathyroid Hormone Diseases Hyperparathyroidism If too much calcium is removed and put in blood, bones become fragile Kidneys excrete calcium; too much can lead to kidney stones If severe, bones undergo massive destruction. Likely to experience spontaneous fractures.

Be ready to answer! Why is iodine important for proper thyroid function? Some thyroid diseases are autoimmune. What does “autoimmune” mean? Which hormone is hypercalcemic (increases blood calcium levels)? Which gland makes it? Which hormone is hypocalcemic (decreases blood calcium levels)? Which gland makes it? How are the thyroid and parathyroids linked anatomically?