Box 1.

Glossary of abbreviations and important terms used in this paper.

TSH – Thyroid Stimulating Hormone/Thyrotropin

TRH – Thyrotropin Releasing Hormone

FT4 – free thyroxine

FT3 – free triiodothyronine

tsh level – a mathematical abstraction representing what the TSH level would be in the absence of autoregulation

r – a term to demonstrate the relationship between TSH and tsh levels. TSH level = r.tsh level

TSH curve – the graph representing the physiological hypothalamo- pituitary response to FT4, i.e. a progressive decline in TSH levels as FT4 levels are increased

tsh curve – a mathematical abstraction representing what the TSH curve would be in the absence of autoregulation

p – proportion of tsh remaining after a reduction to thyrotroph number and/or secretory function

LH – Luteinising Hormone

FSH – Follicle Stimulating Hormone

ACTH – Adrenocorticotropic Hormone