Prolactin and Male Fertility: The Long and Short Feedback Regulation

Table 5

Diurnal hormone variations in adult men.

Hormone/mL	Mean	Circadian	Acrophase (h)	Nadir (h)
	concentration	amplitude	(range)	(range)
T, ng	3.56±1.94^*	3.1±0.8^*	1–5	9–12
E2, pg	55.9±26.9^*	38±7.2^*	15–18	24–2
BLH, mIU	55.4±6.25^*	14.4±2.2^*	9–12	24–2
ILH, mIU	7.4±1.7^*	3±0.6^*	1–5	15–17
BPRL, ng	4.9±1.7^*	2.6±0.4^*	20–23	9–11
IPRL, ng	11.6±2.0^*	4.1±0.8^*	23–4	11–15

Hormones in the hourly blood samples of healthy men were assayed by RIA. Hormone concentration and circadian amplitudes are expressed per milliliter plasma. ^* = SD. T = testosterone; ILH = immunoreactive LH (NIADDK-LER-907); BLH = bioactive LH (WHO 2nd IRP 78/549); BPRL = bioactive PRL (NIAMDD-hPRL-I-6); IPRL = immunoactive PRL (NIAMDD-hPRL-I-6); E₂= 17-β-estradiol [76].