Age 16Age 33Age 52
Maurice Tillet: The French Angel 57
Growth-promoting and metabolic actions of growth hormone (GH).Hypothalamussecretes growthhormone–releasinghormone (GHRH), andGHIH (somatostatin)AnteriorpituitaryInhibits GHRH releaseStimulates GHIH releaseInhibits GH synthesisand releaseFeedbackIndirect actions(growth-promoting)Liver andother tissuesInsulin-like growthfactors (IGFs)ProduceEffectsSkeletalExtraskeletalFatmetabolismCarbohydratemetabolismDirect actions(metabolic,anti-insulin)EffectsGrowth hormone (GH)Increased cartilageformation andskeletal growthIncreased proteinsynthesis, andcell growth andproliferationIncreasedfat breakdownand releaseIncreased bloodglucose and otheranti-insulin effectsIncreases, stimulatesInitial stimulusReduces, inhibitsPhysiological responseResult58
Thyroid-Stimulating Hormone (TSH)•Stimulates the thyroid gland to secrete triiodothyronine (T3) and thyroxine (T4)•Secretion stimulated by thyrotropin-releasing (TRH) from hypothalamus•T3and T4blood level is a major regulator of TRH secretion59
Thyroid Hormone Functions•Thyroid hormones affect quality of life–Have long-term effects on metabolism–Are required for normal growth and development–Are essential for nervous system development•The effects of thyroid hormones are most easily seen in cases of hypersecretion and hyposecretion60
Hyperthyroidism (Chronic High Thyroid Hormone Levels)•Hyperthyroidism has dramatic effects–Increases oxygen consumption and metabolic heat production–Increase protein catabolism and may cause muscle weakness–Hyperexcitable reflexes and psychological disturbances–Influence -adrenergic receptors in the heart (high heart rate and force of contraction)61
Hypothyroidism (Chronic Low Thyroid Hormone Levels)•Hypothyroidism has opposing effects–Slow metabolic rate and oxygen consumption–Decreased protein synthesis–Effects on the nervous system (slowed reflexes, slow speech and thought processes, and feelings of fatigue)•Cretinism in infants–Slow heart rate (bradycardia)62
HypothalamusTRHAnterior pituitaryTSHThyroid glandThyroidhormonesTarget cellsStimulatesRegulation of thyroid hormone secretion.Inhibits63
Goiter: Hypertrophy of the Thyroid Gland•Goiter is due to excessive TSH stimulation of the thyroid gland:1.In hypothyroidism, lack of negative feedback can result in high TSH levels 2.In hyperthyroidism, antibodies can mimic TSH and cause goiterFigure 23-10b64
Goiter can Occur in Both Hypothyroidism and HyperthyroidismFigure 23-12a65
Goiter can Occur in Both Hypothyroidism and HyperthyroidismFigure 23-12b66
Exophthalmus: Hypertrophy of Tissues in the Eye Socket•Sign of hyperthyroidismFigure 23-10c67
Follicle-Stimulating Hormone (FSH)•In females: targets ovaries for monthly development of several ovarian follicles that surround a developing oocyte•In males: targets testes for production of sperm•Secretion stimulated by gonadotropin-releasing (GnRH) hormone from hypothalamus•Blood estrogen or testosterone level is a major regulator of GnRH and FSH secretion68
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