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GCSE Biology · key term
Thyrotropin-releasing hormone, which is produced by the hypothalamus and stimulates the pituitary gland to release TSH.
Used by Edexcel and OCR
Specification 7.3 · Paper 2
Revise: ThyroxineWhen the level of thyroxine is low, the hypothalamus produces more thyrotropin-releasing hormone (TRH). TRH stimulates the pituitary gland to release thyroid-stimulating hormone (TSH) into the blood.
Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Higher), Paper 4 (Higher)
Thyrotropin-releasing hormone, released by the hypothalamus to stimulate the pituitary gland to secrete TSH.
For a sequence question, name each structure as well as each hormone: hypothalamus → TRH → pituitary gland → TSH → thyroid gland → thyroxine.
To explain negative feedback, include both directions: low thyroxine increases stimulation, while thyroxine returning to its normal level inhibits TRH release and TSH production.
Distinguish the hormones clearly: TRH stimulates the pituitary gland, whereas TSH stimulates the thyroid gland.
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When thyroxine is sufficiently high, it inhibits the release of TRH by the hypothalamus. Less TRH means that the pituitary releases less TSH, so the thyroid is stimulated less and secretes less thyroxine. Its concentration then falls towards the normal level.