Thyroid Feedback Loop

Also called

thyroid · thyroxine · T4 and T3 · TSH · TRH · hypothalamus · pituitary gland · negative feedback · feedback loop · hormone regulation · goitre · iodine deficiency · iodised salt · hypothyroidism · basal metabolic rate · endocrine control · थायरॉइड · थायरॉक्सिन · घेंघा

Topics

• The hypothalamus releases TRH, which reaches the pituitary through a short portal blood supply.
• TRH makes the anterior pituitary release TSH, thyroid-stimulating hormone, into the blood.
• TSH makes the thyroid take up iodine and release thyroxine (T4) and triiodothyronine (T3).
• Thyroid hormones set the basal metabolic rate of every cell and support growth and development.
• Negative feedback: high thyroxine in the blood switches off TRH and TSH release, so the level falls back.
• When thyroxine falls, the brake comes off and TSH rises again, holding the level near its set point.
• Without iodine the thyroid cannot make thyroxine; TSH stays high and the gland swells into a goitre.
• Iodised salt supplies the iodine the thyroid needs; too little thyroxine causes cretinism and myxoedema.

About this model

A GLB file of about 458 KB, shown in Lably's 3D viewer and, on a phone, placed in your room with AR. Credit: Model, science and animation: Lably (built procedurally with three.js; no downloaded meshes). | CC BY 4.0. Original geometry and animation made for Lably.

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