Loucks and Thuma 2003, energy availability and LH pulsatility

Controlled laboratory study in regularly menstruating women showing that luteinising hormone pulsatility is disrupted when energy availability falls below about 30 kcal/kg fat-free mass per day for five days. This established the widely cited ~30 kcal/kg FFM/day threshold for endocrine disruption. Moderate; small mechanistic study, and later work argues the threshold is an individual gradient rather than a sharp cut-off.