Circadian Periodicities of Serum Androgens, Progesterone, Gonadotropins and Luteinizing Hormone-Releasing Hormone in Male Rats: The Effects of Hypothalamic Deafferentation, Castration and Adrenalectomy1

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Abstract
Serum testosterone (T), dihydrotestosterone (DHT), progesterone (P), LH [luteinizing hormone], FSH [follicle stimulating hormone] and luteinizing hormone-releasing hormone (LHRH) levels and the LHRH content in the medial basal hypothalamus (MBH) and preoptic area (POA) were estimated during a 24 h period. Circadian rhythms, temporally unrelated to each other, were evident in serum FSH and LHRH and the MBH LHRH content; serum LH fluctuated randomly. Serum T and DHT demonstrated a parallel circadian pattern while serum T and P appeared inversely related. Serum P rhythm persisted in long-term castrate males. Without adversely affecting serum LH, anterior hypothalamic deafferentation abolished both serum T and P rhythms, whereas adrenalectomy obliterated only the serum T periodicity. The POA-MBH [medial basal hypothalamus] complex and the adrenals play important roles in the circadian regulation of testicular secretions.