Table 2.

Characteristic phenotypical changes of thyroid-stimulating hormone (TSH) and various classical and non-classical thyroid hormones in certain allostatic situations show nearly opposing changes in type 1 and type 2 allostatic load (61, 63, 111, 123, 170–182).

	TSH	FT4	TT4	FT3	TT3	rT3
Type 1 allostasis in fetal period, acute and chronic critical illness, and in deprivation of energy
Fetal life	↓, → or ↑	↓	↓	↓	↓	↑
Caloric deprivation	→ or ↓	→	↓	↓	↓	↑
Exhausting exercise	→ or ↓	→	↓	↓	↓	↑
Critical illness (general)	→ or ↓	→	→ or ↓	↓	↓	→ or ↑
Chronic heart failure	→ or ↓	→	→ or ↓	↓	↓	→ or ↑
Renal diseases	→	→ or ↓	→ or ↓	→	↓	→
Liver diseases	→	→ or ↓	↑	↓	→ or ↑	→ or ↑
Pulmonary diseases	→	→	→	↓	→	→ or ↑
Diabetes mellitus	→ or ↓	→ or ↑	↓	↓	↓	→ or ↑
Sepsis	↓	→	→ or ↓	↓	↓	→ or ↑
HIV infection	→	→ or ↓	→	→ or ↓	→	→ or ↓
Depression	→	→ or ↑	↑	↓	↓	→ or ↑
Type 2 allostasis-related conditions
Pregnancy	→ or ↓	→	↑	→	↑	→
Endurance training	↓, → or ↑	↑	↑	↑	→ or ↓	↑
Obesity	↑	→ or ↓	→ or ↑	↑	↑	→ or ↓
Adaptation to cold	↓, → or ↑	↑	↓, → or ↑	↑	↑	→ or ↓
Acute schizophrenia	→ or ↑	→ or ↑	↑	→ or ↑	↑	→
Post-traumatic stress disorder	→	→	↑	↑	↑	?

FT4 and FT3, free T4 and T3, respectively; TT4 and TT3, total (free + protein-bound) T4 and T3, respectively; rT3, reverse T3; TSH, thyroid-stimulating hormone.

Hormone concentration unchanged (→), increased (↑), decreased (↓), or not reported (?). Small studies also reported increased concentrations of 3,5-diiodothyronine (3,5-T2) (61–63), triiodothyroacetate and tetraiodothyroacetate (123, 124), and decreased concentrations of 3-monothyronamine (63) in critical illness and chronic heart failure (not shown in table). See text for definition of type 1 and type 2 allostasis in the context of pituitary–thyroid function.