Low FSH levels: problems and conditions

Follicle Stimulating Hormone (FSH), member of gonadotropin family, which includes also the Luteinizing Hormone (LH) and the Human Chorionic Gonadotropin (hCG) is critical for follicular maturation and ovarian steroidogenesis (production of steroids). Both men and women produce this hormone in different amounts.

It helps women release their eggs during ovulation and men to make sperm.

Not producing enough of this hormone can result in difficulties getting pregnant. On the other hand, having too much of it can also cause the same problem. The effects of gonadotropins may not be limited only to endocrine and reproductive functions. In fact, excessive gonadotropin stimulation of the ovarian epithelium has been postulated to be one of the possible mechanisms responsible for the appearance of ovarian cancer. However, studies that directly examined the association between blood levels of gonadotropins and ovarian cancer risk, do no support fully this theory. After the menopause, FSH levels gradually increase through negative feedback as a result of the end of the ovarian function. Given the important fluctuation of FSH levels even under normal physiological conditions, determination of FSH in a single measurements may provide inadequate estimates of the real average values over extended periods of time (one of the reasons why, for example, FSH blood or urine tests alone aren’t worth much if you want to test wether you are peri/menopausal). In fact variation on FSH levels during the menstrual cycle is thought to be critical in the mechanism of FSH-dependent selection of the dominant follicles (the follicle that will mature to releases the egg) and could affect the reliability estimates in premenopausal women.

Although the ovarian function markedly decreases after the menopause, gonadotropins may still play a role in postmenopausal women.

Ovarian tissues from postmenopausal women still express gonadotropin receptors and therefore could produce steroid hormones. It has been shown that the postmenopausal ovary is characterized by a decreased secretion of oestrogens and certain androgens, but the secretion of testosterone is preserved to a large extent in most postmenopausal women. These observations suggest that gonadotropin response and endocrine function do not entirely cease after the menopause and may play a role in certain hormone-dependent conditions, such as polycystic ovaries.

There are several conditions in which FSH level are decreased for example, progesterone-negative amenorrhea, hyperprolactinemy, anorexia nervosa, Kallmann syndrome (olfacto-genitale syndrome), trauma, tumour. We all know what tumours, trauma, and anorexia nervosa are about. So let’s have a closer look into the other conditions.

Progesterone-negative amenorrhea

One of the causes of this condition could be elevated levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) which would be the signs of ovarian failure. There are rare circumstances in which LH and FSH are elevated but the ovaries still contain follicles (resistant ovary syndrome). However in most cases, if the gonadotropins (LH, FSH) are elevated, premature ovarian failure is likely to be diagnosed. If there are no contraindications, hormonal replacement therapy (HRT) should be used especially in premature ovarian failure to avoid the long-term effects of oestrogen deficiency.


Hyperprolactinemia can cause 20% of cases of secondary amenorrhea, and therefore unbalance in FSH and LH. Although galactorrhea may indicate this diagnosis, its absence does not represent a good sign, and all patients should be screened with a serum prolactin level. Several physiologic and pharmacologic events can alter prolactin levels. Increased levels can occur from stress, either physical or emotional. Levels should not be measured after a recent breast examination because even breast stimulation can increase blood prolactin levels. Prolactin can also be increased by many medications, including oral contraceptives, estrogens, phenothiazines, antidepressants, metoclopramide and benzodiazepines. The prolactin levels in the serum usually should be <100 ng/ml if from one of these causes. If levels remain elevated after excluding all these listed above, it might be necessary to investigate further.

Kallmann syndrome

This is a genetic disorder that prevents a person from starting or fully completing puberty. Kallmann syndrome is part of a group of conditions termed hypogonadotropic hypogonadism. To distinguish it from other forms of hypogonadotropic hypogonadism, Kallmann syndrome has the additional symptom of a total lack of sense of smell or, in some cases a reduced sense of smell. If the genetic disorder is left untreated, people will have for sure poorly defined secondary sexual characteristics, will show signs of hypogonadism, they will almost invariably be infertile and also are at increased risk of developing osteoporosis for the lack of hormones. The underlying cause of this genetic disorder is a failure in the correct production or in the activity of gonadotropin-releasing hormone by the hypothalamus. This results in low levels of the sex hormones, testosterone in males or oestrogen and progesterone in females. This influences also the levels of FSH and LH. Diagnosis normally occurs during teenage years when puberty fails to start normally. To treat this condition, lifelong treatment for both sexes is normally required. Hormone replacement therapy (HRT) is the major form of treatment aiming to replace the missing testosterone or oestrogen and progesterone.

Therefore, if you are trying to understand whether measuring FSH levels could give you some better insight, reality is, that there is not a straight forward answer. Moreover, if you have one of the condition listed above, your FSH levels could be anyway altered or fluctuating. Be aware that FSH plasma level measurements are able to give you a clear answer only once you reach post-menopausal state, because before its level is still fluctuating.  



Nancy A. Curosh MD, in Decision Making in Medicine (Third Edition), 2010

Int J Impot Res. 2000 Apr;12(2):121-3. Kallmann’s syndrome: clues to clinical diagnosis. John H, Schmid C.

Amenorrhea, Secondary. Megan Lord; Manjusha Sahni.

Arslan AA, Zeleniuch-Jacquotte A, Lukanova A, Rinaldi S, Kaaks R, Toniolo P. Reliability of follicle-stimulating hormone measurements in serum. Reprod Biol Endocrinol. 2003;1:49. Published 2003 Jun 18. doi:10.1186/1477-7827-1-49

By Ornella Cappellari