Endocrine System

endocrine glands act on cells in ___________ organs, which is different than autocrine or paracrine factors

distant

insulin is a _______ soluble hormones

water

steroids are ________ soluble hormones

fat

where do water soluble hormones bind?

receptors on the surface of the target cell

where do fat soluble hormones bind?

receptors inside of the cells (nucleus), passing through the plasma membrane

autocrine signaling

target sites on the same cell

paracrine signaling

target sites on adjacent cells

how do endocrine diseases mainly present clinically?

hyperfunction or hypofunction of the gland

examples of hyposecretion of hormones

1. agenesis

2. atrophy

3. destruction

examples of hypersecretion of hormones

1. tumor

2. hyperplasia

increased cortisol release has negative feedback to which organs?

1. anterior pituitary

2. hypothalamus

the optic chiasm is in very close proximity to what gland?

pituitary gland

where is the pituitary gland located?

in the sella turcica at the base of the brain, connected by a stalk to the hypothalamus

the anterior pituitary connected to the hypothalamus by the __________ portal blood system (2 capillary beds)

hypophyseal

the ___________ pituitary connects directly to the hypothalamus

posterior

the pituitary is known as the __________ gland since it produces hormones that directly affect other endocrine glands

master

the hypothalamus releases factors into the portal vessels that stimulate cells of the _____________ to produce 6 major hormones

anterior lobe

thyroid releasing factor (TRF) induces cells of the anterior pituitary to make _________________ that acts on the thyroid to produce thyroid hormone

thyroid stimulating hormone (TSH)

the hypothalamus makes oxytocin and vasopressin and directly transports these hormones to the ______________ for storage and release

posterior lobe

6 major hormones produced by the anterior pituitary

1. ACTH

2. GH

3. FSH

4. LH

5. TSH

6. prolactin

ACTH stimulates the production of what hormone?

corticosteroids

GH stimulates what kind of growth?

bone and tissue

FSH stimulates what kind of growth?

1. spermatogenesis

2. follicle development

LH stimulates what kind of activity?

1. follicle development

2. ovulation

3. testosterone

______ causes thyroid to make thyroid hormone

TSH

_______ causes adrenal cortex to make cortisol

ACTH

______ stimulates bone and muscle growth

GH

___________ stimulates breast lobules to produce milk

prolactin

______ and ______ are both made by the same anterior lobe cell and both act on the ovaries and testes

LH, FSH

function of oxytocin

1. social bonding (cuddle hormone)

2. uterine contractions during birth

function of vasopressin (antidiuretic hormone)

regulates water retention in kidney

what is the primary cause of pituitary hyperfunction?

pituitary adenomas

pituitary adenomas

benign tumors derived from the different anterior lobe cells

adenomas can be __________ or ___________

functional, non-functional

functional pituitary adenomas

secrete the specific hormone

non-functional pituitary adenomas

don’t secrete hormone, but the tumor mass, if large enough, can compress and damage brain tissue

the most common adenomas derive from cell types that produce which hormones?

1. ACTH

2. GH

3. prolactin

adenomas secreting growth hormone can result in ________________ (if it occurs before puberty) or __________ in an adult

pituitary gigantism, acromegaly

pituitary gigantism results in very tall people over __________

8 feet

acromegaly

1. increased growth of bone and soft tissue causing characteristic features

2. large jaw and brow

3. bony spurs in spine

4. large “soft and doughy” hands

5. metabolic issues that shorten lifespan

how can large adenomas cause vision problems and headaches?

they can have a “mass effect” and compress the nearby optic chiasm

major causes of pituitary hypofunction

1. non-functional (non-secretory) adenoma

2. ischemia of pituitary gland

the major cause of ischemia of the pituitary gland is __________

blood loss

obstetrical hemorrhage

1. massive blood loss during childbirth

2. causes ischemia and pituitary hypofunction

the pituitary gland is highly vascularized, and this increases during ___________, making it much more susceptible to ischemia

pregnancy

Sheehan’s pituitary necrosis (Sheehan syndrome)

a medical emergency with ischemia and pituitary hypofunction during massive blood loss from childbirth

where is the thyroid gland located?

lower neck surrounding the trachea

the thyroid gland is highly ____________ and has 2 lobes connected by an isthmus

vascularized

euthyroid

normal thyroid function

hyperthyroid

produces excessive thyroid hormone

toxic thyroid

very high levels of thyroid hormone

hypothyroid

produced inadequate amounts of thyroid hormone

what is the functional unit of the thyroid gland?

thyroid follicle

follicular epithelial cells (thyrocytes) surround a pool of __________ that contains thyroglobulin

colloid

thyroglobulin

precursor of thyroid hormone made by thyrocytes

parafollicular cells (C cells)

2% of thyroid cells, located between the follicles and produce the hormone calcitonin

calcitonin

decreases blood calcium levels by opposing the action of parathyroid hormone (PTH)

there is an extensive __________ network in the connective tissue between follicle cells of the thyroid gland

capillary

___________ is an essential dietary mineral needed for thyroid hormone production

iodine

blood iodine is trapped by thyroid follicular cells which ____________ that mineral in the thyroid gland

concentrate

thyroglobulin binds ___________ and is stored in the colloid

iodine

when thyroid hormone is needed, the pituitary releases TSH into the blood which binds receptors on ____________ cells, causing the cells to reabsorb _____________ from the colloid and generate thyroid hormone

follicular, thyroglobulin

thyroxine (T4, 4 iodine molecules)

stable precursor hormone, and almost all cells convert it to the active form T3 (3 iodine molecules) needed for metabolism in all tissues

high T3/T4 levels in blood inhibit _______ release

TSH

increased levels of thyroid hormones signal to the ___________ to stop secreting TSH

hypothalamus

thyroid goiters involve an ______________ of the gland

enlargement

diffuse goiter

gland is uniformly large with many different causes

what is the major cause of diffuse goiters worldwide?

iodine deficiency

uni-nodular goiter

single enlarged nodule, caused by tumors or cysts

multi-nodular goiter

many enlarged nodules of varying sizes, usually caused by autoimmune thyroiditis (both hyper and hypo) or tumors

hyperthyroidism affects ___________ more often

females

graves’ disease accounts for ____% of hyperthyroidism incidents

85

hyperfunctioning follicular adenomas account for ____% of hyperthyroidism incidents

10

5% of hyperthyroidism is considered ___________

idiopathic

graves’ disease

1. autoimmune disease

2. IgG antibody binds to TSH receptor on thyroid cells

3. mimics action of TSH

4. constant production of thyroid hormone

hyperfunctioning follicular adenomas

benign tumors of follicular cells that produce large amounts of thyroid hormone

what are hyperfunctioning follicular adenomas also called?

toxic adenomas

histology of hyperthyroidism

1. follicles are smaller and no longer round due to excessive production of thyroid hormone

2. “drains the colloid lake” of thyroglobulin

clinical features of thyroid hyperfunction (all related to hyper-metabolism)

1. restlessness

2. sweating

3. nervousness

4. heart issues

5. weight loss

6. diarrhea

7. thinning hair

exophthalmos

1. bulging eyes

2. most consistent finding for graves’ disease

thyroid dermopathy

1. indurated skin caused by edema in pretibial region of lower legs

2. clinical feature of graves’ disease

hypothyroidism occurs more often in __________

females

causes of hypothyroidism

1. hashimoto’s thyroiditis

2. infectious thyroiditis

3. iodine deficiency

4. congenital defects

5. medications

hashimoto’s thyroiditis

1. autoimmune destruction of thyroid follicles

2. reduced production of thyroid hormone

3. mild to severe

4. most common cause of hypothyroidism

infectious thyroiditis

1. viral or bacterial

2. thyroid dumps whole supply of stored hormone into blood at once

3. brief but severe hyperthyroidism, followed by prolonged hypothyroidism

4. then normal (euthyroid) function

what is the most common cause of hypothyroidism worldwide, but less common in the US?

iodine deficiency

clinical features of hypothyroidism

1. sluggishness

2. fatigue

3. slow heart rate

4. weight gain

5. edema

6. cold intolerance

7. constipation

8. hair loss and muscle weakness

__________ tumors of the thyroid are more common

benign

follicular adenomas are _________ tumors

benign

types of malignant tumors of the thyroid

1. papillary carcinoma

2. follicular carcinoma

3. anaplastic carcinoma

4. medullary carcinoma

what is the most common malignant tumor of the thyroid?

papillary carcinoma

papillary carcinoma

1. from follicular epithelial cells (thyrocytes)

2. low-grade, slow growing

3. excellent prognosis

follicular carcinoma

1. from follicular epithelial cells

2. more aggressive than papillary carcinomas

3. still good prognosis

anaplastic carcinoma

1. from follicular epithelial cells

2. highly aggressive

what is one of the most lethal types of cancer?

anaplastic carcinoma of thyroid

medullary carcinoma

1. from parafollicular cells (C cells)

2. families with MEN (multiple endocrine neoplasia syndrome)

3. older adults

4. 5 year survival rate of 50%

5. good prognosis with early detection

parathyroid gland

1. usually 4 glands on posterior thyroid

2. makes and releases parathyroid hormone (PTH)

parathyroid hormone (PTH)

1. opposes action of calcitonin

2. triggered by low blood calcium

3. acts to reabsorb calcium from bone and increase retention in kidney

causes of hyperparathyroidism

1. benign adenoma

2. glandular hyperplasia

clinical features of hyperparathyroidism

1. high blood calcium (hypercalcemia)

2. kidney stones

3. muscle weakness

4. bone pain