Prolactin and Weight Gain
Prolactin, a hormone responsible for milk production in breastfeeding mothers, may indirectly contribute to weight gain. However, breastfeeding is generally associated with weight loss, so any weight gain experienced may not be attributable to high prolactin. As we discuss, the relationship between prolactin and weight is complex and influenced by various factors.
What is Prolactin?
Prolactin is a hormone produced mainly by the pituitary gland, specifically by the lactotroph cells in the front part of the pituitary [1]. The name is derived from 'pro-lactation', as it is primarily known for promoting milk production in female mammals [2, 3, 4]. Prolactin concentrations peak during breastfeeding and are associated with oxytocin release when the infant nurses.
Prolactin has multiple roles in the body, including:@Cell proliferation, development, and maturation
- Regulating immune responses
- Pancreatic development
- Modulation of sexuality, arousal, and sexual behavior [2]
- Maternal behaviour
- Cognitive processes [3]
- Neuroprotection [3]
Beyond the pituitary gland, prolactin is produced by many tissues and cells throughout the body [5, 6, 7]. For example, it can be produced by lymphocytes, the immune blood cells [5]. Therefore it can be found in multiple bodily fluids, including blood plasma and cerebrospinal fluid (CSF) [8, 9]. This is useful to be able to measure prolactin levels in the body.
Prolactin and Weight Gain
Several studies have linked elevated prolactin to weight gain and obesity [10].
Prolactinoma is the condition best demonstrating the effects of prolactin on weight gain. It is a benign tumor of the pituitary gland that leads to the production of excess prolactin but no other hormones. Patients with this tumor had a higher BMI, more cholesterol and insulin in the blood, and a higher waist-to-hip circumference ratio (an indicator of weight deposition) [10].
Another study noted that weight gain was a common symptom at the onset of prolactinomas in many women [11]. Furthermore, the amount of prolactin released was proportional to the visceral fat women have highlighted in a 2004 review.
On the other hand, in a retrospective study of prolactinoma patients, 70% of the patients lost weight with the prolactinoma [12].
Therefore, the relationship between prolactin and weight gain is complex, and a consensus has not been reached yet. While some studies suggest a link, others have found no significant effect of prolactin on weight gain [13]. More research is needed to fully understand the role of prolactin in weight regulation.
Prolactin and Breastfeeding
Prolactin plays a crucial role in milk production during breastfeeding. During pregnancy, the concentration of circulating prolactin increases, reaching 10 to 20 times the normal amounts by the end of gestation [14]. However, the effects of prolactin on milk secretion are inhibited by elevated levels of progesterone. Once progesterone and estrogen levels decrease after childbirth, prolactin can stimulate milk production [14].
The highest prolactin levels are observed on days 2-4 following delivery [15]. During breastfeeding, prolactin levels in the blood increase in response to nipple stimulation [16]. This response is essential for maintaining lactation [17]. The prolactin response to suckling can vary widely among individuals and is influenced by breastfeeding frequency [18].
Prolactin is also present in breast milk. During suckling, the milk at the beginning of a feeding contains significantly more prolactin than the milk at the end [19]. The prolactin concentration in milk is related to the degree of fullness of the breast, with the concentration being highest when the breast is full [16].
As lactation is established, prolactin levels decrease, but nursing continues to stimulate prolactin release from the pituitary, promoting continued milk production [14]. However, the prolactin response to suckling declines significantly only after the return of menses, so several months postpartum [17].
Weight Gain and Breastfeeding
Due to the high energy expenditure required, breastfeeding is often associated with postpartum weight loss in mothers. However, some mothers may experience weight gain or stalled weight loss during breastfeeding [20]. This can be attributed to various factors, including hormonal changes and extra calorie intake to meet the demands of milk production [21]. Postpartum depression can also be a cause of weight gain and may impact breastfeeding behavior and breast milk supply.
It's important to note that the relationship between breastfeeding and weight change can vary greatly among individual mothers. The impact of breastfeeding on infant weight gain is an entirely different topic. Infant weight gain is favorable, as it shows growth and development. A few cases have reported weight gain in exclusively breastfed infants, which may be attributed to breastfeeding frequency or breast milk composition [22, 23].
Need more advice?
If you have concerns about weight gain while breastfeeding, it's best to consult with a healthcare professional for personalized advice