Clinical background:
Follicle stimulating hormone (FSH) is a glycoprotein produced by the basophil cells of the anterior pituitary under the control of the hypothalamic Gonadotropin Releasing Hormone. FSH in females of reproductive age promotes the growth and development of the ovarian follicles in the early part of the menstrual cycle. Ovulation is initiated by the midcycle surge of luteinising hormone (LH). A mature ovum is released into the uterine tube and is ready for fertilisation. The ruptured wall of the follicle continues to secrete progesterone and oestradiol until regression which is toward the end of the cycle. It appears that the production of the oestradiol controls the circulating levels of FSH by negative feedback at the hypothalamus.
In the male, FSH, LH, and testosterone are required for maintaining spermatogenesis in the semeniferous tubules of the testes. Testosterone and oestradiol, which are secreted by the Leydig cells of the testes, then act in the control of circulating levels of FSH.
The clinical utility of FSH determination (and that of LH) is in the investigation of function of the hypothalamic-pituitary-gonadal axis.
Specimen container paediatric:
Serum (SST or plain tube)
Specimen container adult:
Serum (SST or plain tube)
Minimum volume paediatric:
0.5 mL
Minimum volume adult:
1 mL blood
Sample stability:
Unseparated sample: 7 days
Separated sample: 2 weeks at 15-25C; 2 weeks at 2-8C; 1 year at -20C
Transport requirements:
Ambient
Interpretation:
Elevated FSH concentrations are associated with primary gonadal failure. FSH concentrations also increase after the menopause in women. Low FSH concentrations may be associated with hypogonadotrophic hypogonadism (i.e. GnRH deficiency) or due to suppression of GnRH secretion due to high concentrations of testosterone in men (e.g. in testosterone replacement therapy) or oestrogens in women (e.g. due to exogenous oestrogens or pregnancy).
Reference ranges:
Male:
1.5 – 12.4 IU/L
Female:
Follicular: 3.5 – 12.5 IU/L
Luteal: 1.7 – 7.7 IU/L
Ovulation: 4.7 – 21.5 IU/L
Postmenopausal: 25.8 – 134.8 IU/L