Pathology 3500 Lecture Notes - Lecture 24: Pituitary Adenoma, Basal Metabolic Rate, Hyperfunction
1 May 2018
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Lecture 009: Endocrine Disease II
Posterior Pituitary Hyper/Hypofunction
● Too much ACTH release
○ Cancer cells (adenomas) produce this hormone
○ Cushing’s Syndrome
○ Hypertension
● Too little ACTH release
● Lead to diabetes
● Addison disease
Summary
● Anterior Pituitary
○ Hyperfunction: adenomas (PRL, GH)
■ Micro or macroadenomas, may be clinically silent or null cell adenoma
○ Hypofunction most common cause tumors
■ Chemical, ablation (surgery or radiation), trauma, other lesion
(inflammation, metastases)
● Posterior Pituitary
○ Hypertension - syndrome of inappropriate ADH (SIADH) secretion
Thyroid Function
● Produces 3 hormones under TSH stimulation
○ Thyroid follicular cells, produces 2 hormones from precursor thyroglobulin
■ T4 (thyroxine/tetraiodothyronine)
■ T3 (triiodothyronine)
○ C cells involved in calcium homeostasis
■ Calcitonin
● T3 and T4 enter circulation
○ Mostly bound to transport proteins
■ Concentration of free (i.e. unbound) T3 and T4 is tightly regulated
○ Secreted T3 and T4 inhibit release of TRH and TSH from the hypothalamus and
pituitary
● Free T4 (prohormone) is largely converted to T3 (active hormone) via deiodinase
● Thyroid hormone receptor complex binds thyroid hormone response elements (TREs) to
target gene
○ Serve to increase basal metabolic rate
■ Increase lipid and carb metabolism
■ Promote protein synthesis
Hypothalamic Pituitary Thyroid Axis
● Negative feedback
○ Active hormone
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Thyroid
● Follicles lined by thyroglobulin
● Need iodine
Hyperthyroidism
● Thyrotoxicosis
○ Excess of thyroid hormone
○ Hypermetabolic state caused by increased T3 and T4 in circulation
● Clinical manifestation
○ Constitution symptoms
■ Heat intolerance, sweating , weight loss, despite increased appetite
○ Hypermotility of the GI tract
■ malalborsptiona and diarrhea
○ Cardiac effect
■ Palpitation, increased RT (tachycardia)
○ Neuromuscular effect
■ Tremor, muscle weakness
○ Ocular effects
■ Upper lid reaction
● Causes of hyperthyroidism
○ Primary causes
■ Graves disease
● Autoimmune condition
■ Hyperfunction multinodular goitre
■ Hyperfunctioning thyroid adenoma
■ Iodine excess (complex pathogenesis)
○ Secondary causes
■ Pituitary adenoma (TSH)
● Lab diagnosis of hyperthyroidism
○ TSH levels are decreased and free T4 (and T3) levels are increased
■ Increased TSH is suggested of a adenoma producing extra TSH
■ Except for pituitary adenoma that secrete TSH
○ Radioactive iodine scans may be useful in determining etiology
Hypothyroidism
● Decreased circulation T3 and T4
○ Abnormality interfering with production of thyroid hormones
● Cretinism
○ Infancy developmental abnormalities of skeletal and CNS
■ Resulting in mental retardation, short stature
● Myxedema
○ Rare cases of long-standing, undiagnosed hypanthodium
○ Potentially life threatening complication
○ Severe cold intolerance, obesity, mental sluggishness, and lethargy
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Micro or macroadenomas, may be clinically silent or null cell adenoma. Chemical, ablation (surgery or radiation), trauma, other lesion (inflammation, metastases) Hypertension - syndrome of inappropriate adh (siadh) secretion. Thyroid follicular cells, produces 2 hormones from precursor thyroglobulin. Concentration of free (i. e. unbound) t3 and t4 is tightly regulated. Secreted t3 and t4 inhibit release of trh and tsh from the hypothalamus and pituitary. Free t4 (prohormone) is largely converted to t3 (active hormone) via deiodinase. Thyroid hormone receptor complex binds thyroid hormone response elements (tres) to target gene. Hypermetabolic state caused by increased t3 and t4 in circulation. Heat intolerance, sweating , weight loss, despite increased appetite. Tsh levels are decreased and free t4 (and t3) levels are increased. Increased tsh is suggested of a adenoma producing extra tsh. Except for pituitary adenoma that secrete tsh. Radioactive iodine scans may be useful in determining etiology. Abnormality interfering with production of thyroid hormones.
