The Anterior Pituitary and Thyroid Gland

Question 1

hypothalamus hormones

Answer 1

peptide neurohormones

gonadotropin releasing hormone (GnRH)

thyrotropin releasing hormone (TRH)

corticotropin releasing hormone (CRH)

growth hormone releasing hormone (GHRH)

dopamine

Question 2

what does gonadotropin releasing hormone (GnRH) act on?

Answer 2

gonadotropin releasing hormone: from hypothalamus acts on anterior pituitary to release

• > luteinizing hormone (LH)
• > follicle stimulating hormone (FSH)

Question 3

what does thyrotropin releasing hormone (TRH) act on?

Answer 3

thyrotropin releasing hormone: from hypothalamus acts on anterior pituitary to release

• > thyroid stimulating hormone (TSH)
• > simulates thyroid growth

Question 4

what does corticotropin releasing hormone (CRH) act on?

Answer 4

corticotropin releasing hormone: from hypothalamus acts on anterior pituitary to release

-> adrenocorticotropic hormone (ACTH)

Question 5

what does growth hormone releasing hormone (GHRH) act on?

Answer 5

growth hormone releasing hormone: from hypothalamus acts on anterior pituitary to release

-> growth hormone (GH)

Question 6

what does dopamine act on?

Answer 6

dopamine: from hypothalamus acts on anterior pituitary to inhibit secretion of prolactin

Question 7

anterior pituitary hormones

Answer 7

peptide hormones

luteinizing hormone (LH)

follicle stimulating hormone (FSH)

thyroid stimulating hormone (TSH)

adrenocorticotropic hormone (ACTH)

growth hormone (GH)

prolactin

Question 8

what does follicle stimulating hormone (FSH) and luteinizing hormone (LH) act on?

Answer 8

target: gonads (testes, ovaries)
testes: testosterone - develop and maintain male sexual characteristics and maturation
ovaries: estrogen - affects development of female sexual characteristics and reproductive development, important for functioning of uterus and breasts; also protects bone health Stimulates the lining of the uterus for fertilization; prepares the breasts for milk production

progesterone - stimulates the lining of the uterus for fertilization; prepares the breasts for milk production

Question 9

what does thyroid stimulating hormone (TSH) act on?

Answer 9

target: thyroid gland

stimulates thyroid growth

thyroid hormone - controls metabolism; also affects growth, maturation, nervous system activity, and metabolism

Question 10

what does adrenocorticotropic hormone (ACTH) act on?

Answer 10

target: adrenal glands

cortisol - stress hormone, glucogenesis in liver, protein degradation of muscle, fat breakdown (lypolysis) of adipose, immune suppression

Question 11

what does growth hormone (GH) act on?

Answer 11

target: various tissues (bones, skeletal muscle, liver, adipose (fat tissue))

Question 12

what does prolactin act on?

Answer 12

target: mammary glands - initiates and maintains milk production in breasts

Question 13

thyroid gland

Answer 13

• > follicles are where the hormone is made (T₃ and T₄) and the thyrogobulin protein
• > colloid central sticky fluid that make up the follicle

Question 14

thyroid hormones

Answer 14

steroid hormones

T₃: triiodothyronine (3 iodide, 1 tyrosine)

T₄: tetraiodithyronine (4 iodide, 1 tyrosine)

Question 15

function of thyroid hormones

Answer 15

target tissue: all body tissues

mechanism of action: change DNA transcription -> translation (make new proteins)

effect on the body: normal growth (children), proper nervous system development, metabolism (basal metabolic rate)

too much thyroid hormone: hyperthyroidism

too little thyroid hormone: hypothyroidism

-> thyroid hormones T3 and T4 inhibit release of TRH and TSH

Question 16

how is T₃/T₄ released?

Answer 16

• > hypothalamus makes and sends thryotropin releasing hormone
• > anterior pituitary is stimulated to release thryoid stimulated hormone
• > thyroid stimulating hormone binds to receptor of thryoid cells to release thyroid hormones

Question 17

how does the thyroid store thyroid hormone?

Answer 17

• > thyroid is a steroid hormone, but the thyroid stores T3/T4 for a couple months
  1. tyrosine are added on a thyroglobulin (made in follicle) long polypeptide chain of amino acids
  2. iodide

Question 18

synthesizing thyroid hormones

Answer 18

1. dietary iodide transported from blood to colloid: active transport
2. the protein thyroglobulin with tyrosines attatched made in the follicle exocytosis into colloid
3. iodide must be added to the tyrosines in thyroid gland
4. thyroglobulin (with T3 and T4) attached moves into follicular cells (endocytosis)
5. T₃ and T₄ released by protein degradation, diffuse to blood (exocytosis)

Question 19

hyperthyroidism

Answer 19

• > goitre (hypertophy)
• > weight loss
• > sensitive to heat
• > fast heart rate
• > nervous, irritable

treatment - surgery, radioactive iodine (consume and turns into iodide), drugs slow production

Question 20

hypothyroidism

Answer 20

• > shrink or too little thyroid (atrophy)
• > slow heart rate
• > sensitive to cold
• > weight gain
• > fatigue, depression

treatment - synthetic thyroxine

Question 21

how does the body over produce thyroid hormones?

Answer 21

• > hypertrophy (more than, growth) (goitre for thyroid)
• > autoimmune disease (antibodies shaped very similar to thyroid stimulating hormone binds to thyroid receptors and over stimulates the thyroid

Question 22

goitre with hypothyroidism

Answer 22

not enough iodine in diet to create thyroid hormones

thyroid hormone inhibits thyrotropin releasing hormone and thyroid stimulating hormone

so the hypothalamus and anterior pituitary gland are constantly stimulated to produce those hormones making the thyroid over grow