Control ofMetabolism

BASAL METABOLIC RATEB.M.R.

Used as a baseline to establish a person’s rate of metabolism.

Roughly measures the rate of energy transformation using controlled conditions

Alert, resting, fasted for 12 hr

Insulin, Sex Hormones, etc affect metabolic rate but do NOT regulate it

The Thyroid Gland

Thyroid hormones regulate BMR, long-term stress, and prolonged exposure to cold

Thyroid HormonesThyroid gland contains follicles that contain

iodine (from blood) and hormone pre-cursors. Hormones are formed by the addition of I to tyrosine (amino acid)

Tyrosine + I M.I.T. (2 I D.I.T.)T4 = 2 DIT’s joined

T3 = 1 MIT + 2 DIT

Receptors for these hormones are in cell nuclei (but they are still a.a. derivatives) T3 works better than T4Alter enzymes involved in specific metabolic pathways (ATP synthase)Increase glucose uptake & glycogen and fatty acid use

CONTROL OF THYROID HOROMONES

Hypothalamus is stimulated to produce TRH by cold, cortisol or the nervous systemsTRH acts on Anterior Pituitary to release TSH which causes the release of T4 & T3 at the Thyroid

DISORDERSGOITER

• Low I diet not enough T4 incr. TSH builds up in thyroid

CRETINISM

• Absence of T3/T4 in early infancy

• Mental retardation & growth metabolism

– Developmental milestones delayed

– Short ‘long’ bones

HYPOTHYROIDISM

• Failure of TSH secretion OR damage to thyroid/lack of I (goiter)

• Reduced BMR

– Fatigue, lethargic

– Cold

– Edema (swelling)

– Reduced cardiac output

– Diminished physical/mental activity

HYPERTHYROIDISM

• Overactive thyroid

• Increased BMR– Hot, irritable, nervous, weight loss, irregular

heartbeat, bulging eyeballs

GRAVES’ DISEASE

Immune system antibodies mimic TSH function